TY  - JOUR
AU  - Stojanović, Danka
AU  - Beličev, Petra
AU  - Radovanović, Jelena V.
AU  - Milanović, Vitomir B.
PY  - 2019
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/8542
AB  - In this work, we have systematically studied the impact of geometric parameters on chiral effects which occur in metamaterial made of Ω elements. The analysis of group delays and electric field enhancements indicate stronger interaction between the structure and right circularly polarized waves. Calculations of optical activity and circular dichroism for different values of geometric parameters, allow us to deduce that the thickness of the wire and the gap size have large influence on these effects. On the other hand, the radius of the wire affects mainly the resonant frequency position which enables frequency tunability. The results indicate that multi-functional design of this chiral metamaterial offers great flexibility for various devices: enantiomeric sensors, circular polarizers and light modulators. © 2019 Elsevier B.V.
T2  - Physics Letters A
T1  - Numerical parametric study of chiral effects and group delays in Ω element based terahertz metamaterial
VL  - 383
IS  - 15
SP  - 1816
EP  - 1820
DO  - 10.1016/j.physleta.2019.02.035
ER  - 

@article{
author = "Stojanović, Danka and Beličev, Petra and Radovanović, Jelena V. and Milanović, Vitomir B.",
year = "2019",
abstract = "In this work, we have systematically studied the impact of geometric parameters on chiral effects which occur in metamaterial made of Ω elements. The analysis of group delays and electric field enhancements indicate stronger interaction between the structure and right circularly polarized waves. Calculations of optical activity and circular dichroism for different values of geometric parameters, allow us to deduce that the thickness of the wire and the gap size have large influence on these effects. On the other hand, the radius of the wire affects mainly the resonant frequency position which enables frequency tunability. The results indicate that multi-functional design of this chiral metamaterial offers great flexibility for various devices: enantiomeric sensors, circular polarizers and light modulators. © 2019 Elsevier B.V.",
journal = "Physics Letters A",
title = "Numerical parametric study of chiral effects and group delays in Ω element based terahertz metamaterial",
volume = "383",
number = "15",
pages = "1816-1820",
doi = "10.1016/j.physleta.2019.02.035"
}

Stojanović, D., Beličev, P., Radovanović, J. V.,& Milanović, V. B.. (2019). Numerical parametric study of chiral effects and group delays in Ω element based terahertz metamaterial. in Physics Letters A, 383(15), 1816-1820.
https://doi.org/10.1016/j.physleta.2019.02.035

Stojanović D, Beličev P, Radovanović JV, Milanović VB. Numerical parametric study of chiral effects and group delays in Ω element based terahertz metamaterial. in Physics Letters A. 2019;383(15):1816-1820.
doi:10.1016/j.physleta.2019.02.035 .

Stojanović, Danka, Beličev, Petra, Radovanović, Jelena V., Milanović, Vitomir B., "Numerical parametric study of chiral effects and group delays in Ω element based terahertz metamaterial" in Physics Letters A, 383, no. 15 (2019):1816-1820,
https://doi.org/10.1016/j.physleta.2019.02.035 . .

TY  - CONF
AU  - Atić, Aleksandar
AU  - Radovanović, Jelena
AU  - Milanović, Vitomir
PY  - 2019
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/10864
AB  - ZnO has been proposed recently as a good base material for high-power terahertz quantum cascade lasers (QCLs) operating at room temperature. We have developed a theoretical model for calculation of the optical gain, based on solving the system of rate equations and taking into account relevant scattering mechanisms. This model has been implemented to perform numerical simulations using ZnO/ZnMgO material combination, starting from the conventional design with three well within the active region of the structure. The influence of the layer widths and composition on the output properties has been considered, together with the variation of the number of quantum wells per QCL period.
PB  - Belgrade : Institute of Technical Sciences of SASA
C3  - Eighteenth Young Researchers' Conference Materials Sciences and Engineering : program and the book of abstracts; December 4-6, 2019; Belgrade
T1  - Modeling of the optical gain in ZnO-based quantum cascade lasers
SP  - 31
UR  - https://hdl.handle.net/21.15107/rcub_vinar_10864
ER  - 

@conference{
author = "Atić, Aleksandar and Radovanović, Jelena and Milanović, Vitomir",
year = "2019",
abstract = "ZnO has been proposed recently as a good base material for high-power terahertz quantum cascade lasers (QCLs) operating at room temperature. We have developed a theoretical model for calculation of the optical gain, based on solving the system of rate equations and taking into account relevant scattering mechanisms. This model has been implemented to perform numerical simulations using ZnO/ZnMgO material combination, starting from the conventional design with three well within the active region of the structure. The influence of the layer widths and composition on the output properties has been considered, together with the variation of the number of quantum wells per QCL period.",
publisher = "Belgrade : Institute of Technical Sciences of SASA",
journal = "Eighteenth Young Researchers' Conference Materials Sciences and Engineering : program and the book of abstracts; December 4-6, 2019; Belgrade",
title = "Modeling of the optical gain in ZnO-based quantum cascade lasers",
pages = "31",
url = "https://hdl.handle.net/21.15107/rcub_vinar_10864"
}

Atić, A., Radovanović, J.,& Milanović, V.. (2019). Modeling of the optical gain in ZnO-based quantum cascade lasers. in Eighteenth Young Researchers' Conference Materials Sciences and Engineering : program and the book of abstracts; December 4-6, 2019; Belgrade
Belgrade : Institute of Technical Sciences of SASA., 31.
https://hdl.handle.net/21.15107/rcub_vinar_10864

Atić A, Radovanović J, Milanović V. Modeling of the optical gain in ZnO-based quantum cascade lasers. in Eighteenth Young Researchers' Conference Materials Sciences and Engineering : program and the book of abstracts; December 4-6, 2019; Belgrade. 2019;:31.
https://hdl.handle.net/21.15107/rcub_vinar_10864 .

Atić, Aleksandar, Radovanović, Jelena, Milanović, Vitomir, "Modeling of the optical gain in ZnO-based quantum cascade lasers" in Eighteenth Young Researchers' Conference Materials Sciences and Engineering : program and the book of abstracts; December 4-6, 2019; Belgrade (2019):31,
https://hdl.handle.net/21.15107/rcub_vinar_10864 .

TY  - JOUR
AU  - Dubajić, Miloš
AU  - Daničić, Aleksandar
AU  - Vuković, Nikola
AU  - Milanović, Vitomir B.
AU  - Radovanović, Jelena V.
PY  - 2018
UR  - http://link.springer.com/10.1007/s11082-018-1639-1
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/7895
AB  - In this work we theoretically investigate a possibility to use cubic nitride based multi-layer periodic nanostructure as a semiconductor metamaterial. The structure design is based on an active region of a quantum cascade laser optimized to achieve optical gain in the Terahertz (THz) spectral range. In particular, we test the GaN/AlGaN quantum well configurations, which should exhibit important advantages compared to GaAs-based structures, namely room temperature operation without the assistance of magnetic field and lower doping densities. Our numerical rate-equations model is solved self-consistently and it takes into account electron-longitudinal optical phonon scattering between all the relevant states among the adjacent periods of the structure. A global optimization routine, specifically genetic algorithm is then used to generate new gain-optimized structures. This work confirms the advantages of cubic GaN designs over GaAs ones, namely feasibility of negative refraction at room temperature without the assistance of magnetic field while keeping the doping densities of the same order of magnitude. © 2018, Springer Science+Business Media, LLC, part of Springer Nature.
T2  - Optical and Quantum Electronics
T1  - Optimization of cubic GaN/AlGaN quantum cascade structures for negative refraction in the THz spectral range
VL  - 50
IS  - 10
SP  - 373
DO  - 10.1007/s11082-018-1639-1
ER  - 

@article{
author = "Dubajić, Miloš and Daničić, Aleksandar and Vuković, Nikola and Milanović, Vitomir B. and Radovanović, Jelena V.",
year = "2018",
abstract = "In this work we theoretically investigate a possibility to use cubic nitride based multi-layer periodic nanostructure as a semiconductor metamaterial. The structure design is based on an active region of a quantum cascade laser optimized to achieve optical gain in the Terahertz (THz) spectral range. In particular, we test the GaN/AlGaN quantum well configurations, which should exhibit important advantages compared to GaAs-based structures, namely room temperature operation without the assistance of magnetic field and lower doping densities. Our numerical rate-equations model is solved self-consistently and it takes into account electron-longitudinal optical phonon scattering between all the relevant states among the adjacent periods of the structure. A global optimization routine, specifically genetic algorithm is then used to generate new gain-optimized structures. This work confirms the advantages of cubic GaN designs over GaAs ones, namely feasibility of negative refraction at room temperature without the assistance of magnetic field while keeping the doping densities of the same order of magnitude. © 2018, Springer Science+Business Media, LLC, part of Springer Nature.",
journal = "Optical and Quantum Electronics",
title = "Optimization of cubic GaN/AlGaN quantum cascade structures for negative refraction in the THz spectral range",
volume = "50",
number = "10",
pages = "373",
doi = "10.1007/s11082-018-1639-1"
}

Dubajić, M., Daničić, A., Vuković, N., Milanović, V. B.,& Radovanović, J. V.. (2018). Optimization of cubic GaN/AlGaN quantum cascade structures for negative refraction in the THz spectral range. in Optical and Quantum Electronics, 50(10), 373.
https://doi.org/10.1007/s11082-018-1639-1

Dubajić M, Daničić A, Vuković N, Milanović VB, Radovanović JV. Optimization of cubic GaN/AlGaN quantum cascade structures for negative refraction in the THz spectral range. in Optical and Quantum Electronics. 2018;50(10):373.
doi:10.1007/s11082-018-1639-1 .

Dubajić, Miloš, Daničić, Aleksandar, Vuković, Nikola, Milanović, Vitomir B., Radovanović, Jelena V., "Optimization of cubic GaN/AlGaN quantum cascade structures for negative refraction in the THz spectral range" in Optical and Quantum Electronics, 50, no. 10 (2018):373,
https://doi.org/10.1007/s11082-018-1639-1 . .

TY  - CONF
AU  - Stojanović, Danka B.
AU  - Beličev, Petra
AU  - Gligorić, Goran
AU  - Radovanović, Jelena V.
AU  - Milanović, Vitomir B.
AU  - Hadžievski, Ljupčo
PY  - 2017
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/12789
PB  - Belgrade : Institute of physics
C3  - 10th Photonics Workshop : Book of abstracts
T1  - Electromagnetic wave propagation through terahertz chiral metamaterials
SP  - 9
EP  - 9
UR  - https://hdl.handle.net/21.15107/rcub_vinar_12789
ER  - 

@conference{
author = "Stojanović, Danka B. and Beličev, Petra and Gligorić, Goran and Radovanović, Jelena V. and Milanović, Vitomir B. and Hadžievski, Ljupčo",
year = "2017",
publisher = "Belgrade : Institute of physics",
journal = "10th Photonics Workshop : Book of abstracts",
title = "Electromagnetic wave propagation through terahertz chiral metamaterials",
pages = "9-9",
url = "https://hdl.handle.net/21.15107/rcub_vinar_12789"
}

Stojanović, D. B., Beličev, P., Gligorić, G., Radovanović, J. V., Milanović, V. B.,& Hadžievski, L.. (2017). Electromagnetic wave propagation through terahertz chiral metamaterials. in 10th Photonics Workshop : Book of abstracts
Belgrade : Institute of physics., 9-9.
https://hdl.handle.net/21.15107/rcub_vinar_12789

Stojanović DB, Beličev P, Gligorić G, Radovanović JV, Milanović VB, Hadžievski L. Electromagnetic wave propagation through terahertz chiral metamaterials. in 10th Photonics Workshop : Book of abstracts. 2017;:9-9.
https://hdl.handle.net/21.15107/rcub_vinar_12789 .

Stojanović, Danka B., Beličev, Petra, Gligorić, Goran, Radovanović, Jelena V., Milanović, Vitomir B., Hadžievski, Ljupčo, "Electromagnetic wave propagation through terahertz chiral metamaterials" in 10th Photonics Workshop : Book of abstracts (2017):9-9,
https://hdl.handle.net/21.15107/rcub_vinar_12789 .

TY  - JOUR
AU  - Daničić, Aleksandar
AU  - Radovanović, Jelena V.
AU  - Ramović, Sabina
AU  - Milanović, Vitomir B.
PY  - 2016
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/927
AB  - In order to avoid losses in metamaterial unit cells at frequencies of interest, caused by metallic inclusions, an active medium design has been proposed. As candidate structures for this active medium, we have chosen quantum cascade lasers because of their high output gain. Here we analyze and compare two quantum cascade structures that emit at 4.6 THz and 3.9 THz, respectively, placed under the influence of a strong magnetic field. We first solve the full system of rate equations for all relevant Landau levels, and obtain the necessary information about carrier distribution among the levels, after which we are able to evaluate the permittivity component along the growth direction of the structure. With these data one can determine the conditions under which negative refraction occurs, and calculate the values of the refractive index of the structure, as well as the range of frequencies at which the structure exhibits negative refraction for a predefined total electron sheet density.
PB  - IOP Publishing Ltd
T2  - Journal of Physics. D: Applied Physics
T1  - Exploring negative refraction conditions for quantum cascade semiconductor metamaterials in the terahertz spectral range
VL  - 49
IS  - 8
DO  - 10.1088/0022-3727/49/8/085105
ER  - 

@article{
author = "Daničić, Aleksandar and Radovanović, Jelena V. and Ramović, Sabina and Milanović, Vitomir B.",
year = "2016",
abstract = "In order to avoid losses in metamaterial unit cells at frequencies of interest, caused by metallic inclusions, an active medium design has been proposed. As candidate structures for this active medium, we have chosen quantum cascade lasers because of their high output gain. Here we analyze and compare two quantum cascade structures that emit at 4.6 THz and 3.9 THz, respectively, placed under the influence of a strong magnetic field. We first solve the full system of rate equations for all relevant Landau levels, and obtain the necessary information about carrier distribution among the levels, after which we are able to evaluate the permittivity component along the growth direction of the structure. With these data one can determine the conditions under which negative refraction occurs, and calculate the values of the refractive index of the structure, as well as the range of frequencies at which the structure exhibits negative refraction for a predefined total electron sheet density.",
publisher = "IOP Publishing Ltd",
journal = "Journal of Physics. D: Applied Physics",
title = "Exploring negative refraction conditions for quantum cascade semiconductor metamaterials in the terahertz spectral range",
volume = "49",
number = "8",
doi = "10.1088/0022-3727/49/8/085105"
}

Daničić, A., Radovanović, J. V., Ramović, S.,& Milanović, V. B.. (2016). Exploring negative refraction conditions for quantum cascade semiconductor metamaterials in the terahertz spectral range. in Journal of Physics. D: Applied Physics
IOP Publishing Ltd., 49(8).
https://doi.org/10.1088/0022-3727/49/8/085105

Daničić A, Radovanović JV, Ramović S, Milanović VB. Exploring negative refraction conditions for quantum cascade semiconductor metamaterials in the terahertz spectral range. in Journal of Physics. D: Applied Physics. 2016;49(8).
doi:10.1088/0022-3727/49/8/085105 .

Daničić, Aleksandar, Radovanović, Jelena V., Ramović, Sabina, Milanović, Vitomir B., "Exploring negative refraction conditions for quantum cascade semiconductor metamaterials in the terahertz spectral range" in Journal of Physics. D: Applied Physics, 49, no. 8 (2016),
https://doi.org/10.1088/0022-3727/49/8/085105 . .

TY  - JOUR
AU  - Stojanović, Danka
AU  - Radovanović, Jelena V.
AU  - Milanović, Vitomir B.
PY  - 2016
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/1019
AB  - Recently, group delay has been proven as a very convenient tool for control of terahertz electromagnetic signals used for filters, waveguides and polarization components. Here, we investigate the propagation of circularly polarised terahertz pulse via analysis of group delays in X particle chiral metamaterial. When varying the geometry of the X particle chiral metamaterial, significant modification of chiroptical effects- optical activity and circular dichroism can be observed. Through the analysis of group delays in the frequency region between 1 and 3 THz we conclude that the right circularly polarised wave is more sensitive to changes in the geometry than the left circularly polarised wave. This result implies that the right circularly polarised wave is responsible for variation of chiroptical effects in these structures and opens up a possibility for potential applications.
PB  - Springer
T2  - Optical and Quantum Electronics
T1  - Influence of the geometry of terahertz chiral metamaterial on transmission group delays
VL  - 48
IS  - 4
DO  - 10.1007/s11082-016-0533-y
ER  - 

@article{
author = "Stojanović, Danka and Radovanović, Jelena V. and Milanović, Vitomir B.",
year = "2016",
abstract = "Recently, group delay has been proven as a very convenient tool for control of terahertz electromagnetic signals used for filters, waveguides and polarization components. Here, we investigate the propagation of circularly polarised terahertz pulse via analysis of group delays in X particle chiral metamaterial. When varying the geometry of the X particle chiral metamaterial, significant modification of chiroptical effects- optical activity and circular dichroism can be observed. Through the analysis of group delays in the frequency region between 1 and 3 THz we conclude that the right circularly polarised wave is more sensitive to changes in the geometry than the left circularly polarised wave. This result implies that the right circularly polarised wave is responsible for variation of chiroptical effects in these structures and opens up a possibility for potential applications.",
publisher = "Springer",
journal = "Optical and Quantum Electronics",
title = "Influence of the geometry of terahertz chiral metamaterial on transmission group delays",
volume = "48",
number = "4",
doi = "10.1007/s11082-016-0533-y"
}

Stojanović, D., Radovanović, J. V.,& Milanović, V. B.. (2016). Influence of the geometry of terahertz chiral metamaterial on transmission group delays. in Optical and Quantum Electronics
Springer., 48(4).
https://doi.org/10.1007/s11082-016-0533-y

Stojanović D, Radovanović JV, Milanović VB. Influence of the geometry of terahertz chiral metamaterial on transmission group delays. in Optical and Quantum Electronics. 2016;48(4).
doi:10.1007/s11082-016-0533-y .

Stojanović, Danka, Radovanović, Jelena V., Milanović, Vitomir B., "Influence of the geometry of terahertz chiral metamaterial on transmission group delays" in Optical and Quantum Electronics, 48, no. 4 (2016),
https://doi.org/10.1007/s11082-016-0533-y . .

TY  - JOUR
AU  - Daničić, Aleksandar
AU  - Radovanović, Jelena V.
AU  - Milanović, Vitomir B.
AU  - Indjin, Dragan
AU  - Ikonić, Zoran
PY  - 2016
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/1102
AB  - We consider the influence of additional carrier confinement, achieved by application of strong perpendicular magnetic field, on inter Landau levels electron relaxation rates and the optical gain, of two different GaAs quantum cascade laser structures operating in the terahertz spectral range. Breaking of the in-plane energy dispersion and the formation of discrete energy levels is an efficient mechanism for eventual quenching of optical phonon emission and obtaining very long electronic lifetime in the relevant laser state. We employ our detailed model for calculating the electron relaxation rates (due to interface roughness and electron-longitudinal optical phonon scattering), and solve a full set of rate equations to evaluate the carrier distribution over Landau levels. The numerical simulations are performed for three- and four-well (per period) based structures that operate at 3.9 THz and 1.9 THz, respectively, both implemented in GaAs/Al0.15Ga0.85As. Numerical results are presented for magnetic field values from 1.5 T up to 20 T, while the band nonparabolicity is accounted for. (C) 2016 Elsevier B.V. All rights reserved.
PB  - Elsevier
T2  - Physica E: Low-dimensional Systems and Nanostructures
T1  - Magnetic field effects on THz quantum cascade laser: A comparative analysis of three and four quantum well based active region design
VL  - 81
SP  - 275
EP  - 280
DO  - 10.1016/j.physe.2016.03.019
ER  - 

@article{
author = "Daničić, Aleksandar and Radovanović, Jelena V. and Milanović, Vitomir B. and Indjin, Dragan and Ikonić, Zoran",
year = "2016",
abstract = "We consider the influence of additional carrier confinement, achieved by application of strong perpendicular magnetic field, on inter Landau levels electron relaxation rates and the optical gain, of two different GaAs quantum cascade laser structures operating in the terahertz spectral range. Breaking of the in-plane energy dispersion and the formation of discrete energy levels is an efficient mechanism for eventual quenching of optical phonon emission and obtaining very long electronic lifetime in the relevant laser state. We employ our detailed model for calculating the electron relaxation rates (due to interface roughness and electron-longitudinal optical phonon scattering), and solve a full set of rate equations to evaluate the carrier distribution over Landau levels. The numerical simulations are performed for three- and four-well (per period) based structures that operate at 3.9 THz and 1.9 THz, respectively, both implemented in GaAs/Al0.15Ga0.85As. Numerical results are presented for magnetic field values from 1.5 T up to 20 T, while the band nonparabolicity is accounted for. (C) 2016 Elsevier B.V. All rights reserved.",
publisher = "Elsevier",
journal = "Physica E: Low-dimensional Systems and Nanostructures",
title = "Magnetic field effects on THz quantum cascade laser: A comparative analysis of three and four quantum well based active region design",
volume = "81",
pages = "275-280",
doi = "10.1016/j.physe.2016.03.019"
}

Daničić, A., Radovanović, J. V., Milanović, V. B., Indjin, D.,& Ikonić, Z.. (2016). Magnetic field effects on THz quantum cascade laser: A comparative analysis of three and four quantum well based active region design. in Physica E: Low-dimensional Systems and Nanostructures
Elsevier., 81, 275-280.
https://doi.org/10.1016/j.physe.2016.03.019

Daničić A, Radovanović JV, Milanović VB, Indjin D, Ikonić Z. Magnetic field effects on THz quantum cascade laser: A comparative analysis of three and four quantum well based active region design. in Physica E: Low-dimensional Systems and Nanostructures. 2016;81:275-280.
doi:10.1016/j.physe.2016.03.019 .

Daničić, Aleksandar, Radovanović, Jelena V., Milanović, Vitomir B., Indjin, Dragan, Ikonić, Zoran, "Magnetic field effects on THz quantum cascade laser: A comparative analysis of three and four quantum well based active region design" in Physica E: Low-dimensional Systems and Nanostructures, 81 (2016):275-280,
https://doi.org/10.1016/j.physe.2016.03.019 . .

TY  - JOUR
AU  - Stojanović, Danka
AU  - Radovanović, Jelena V.
AU  - Milanović, Vitomir B.
PY  - 2016
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/1215
AB  - We investigate the propagation of circularly polarized electromagnetic waves through a free-standing Omega particle chiral metamaterial slab and study the associated delay times: dwell time and group delay. Through this analysis, we observe different interactions of right- and left-circularly polarized waves in the terahertz frequency range (1-2.5 THz) with the resonant elements. As a consequence, the resonant-frequency group delay and dwell time of the right-circularly polarized wave are one or more orders of magnitude longer than those of the left. In addition, we compare the delay times obtained from rigorous numerical simulations with those calculated using the retrieved effective parameters. We find that the dwell time cannot be evaluated correctly from the effective medium approximation, while no such problems exist in the case of group delay.
T2  - Physical Review A
T1  - Delay times in a terahertz chiral metamaterial slab
VL  - 94
IS  - 2
DO  - 10.1103/PhysRevA.94.023848
ER  - 

@article{
author = "Stojanović, Danka and Radovanović, Jelena V. and Milanović, Vitomir B.",
year = "2016",
abstract = "We investigate the propagation of circularly polarized electromagnetic waves through a free-standing Omega particle chiral metamaterial slab and study the associated delay times: dwell time and group delay. Through this analysis, we observe different interactions of right- and left-circularly polarized waves in the terahertz frequency range (1-2.5 THz) with the resonant elements. As a consequence, the resonant-frequency group delay and dwell time of the right-circularly polarized wave are one or more orders of magnitude longer than those of the left. In addition, we compare the delay times obtained from rigorous numerical simulations with those calculated using the retrieved effective parameters. We find that the dwell time cannot be evaluated correctly from the effective medium approximation, while no such problems exist in the case of group delay.",
journal = "Physical Review A",
title = "Delay times in a terahertz chiral metamaterial slab",
volume = "94",
number = "2",
doi = "10.1103/PhysRevA.94.023848"
}

Stojanović, D., Radovanović, J. V.,& Milanović, V. B.. (2016). Delay times in a terahertz chiral metamaterial slab. in Physical Review A, 94(2).
https://doi.org/10.1103/PhysRevA.94.023848

Stojanović D, Radovanović JV, Milanović VB. Delay times in a terahertz chiral metamaterial slab. in Physical Review A. 2016;94(2).
doi:10.1103/PhysRevA.94.023848 .

Stojanović, Danka, Radovanović, Jelena V., Milanović, Vitomir B., "Delay times in a terahertz chiral metamaterial slab" in Physical Review A, 94, no. 2 (2016),
https://doi.org/10.1103/PhysRevA.94.023848 . .

TY  - JOUR
AU  - Radosavljević, Ana
AU  - Radovanović, Jelena V.
AU  - Milanović, Vitomir B.
AU  - Indjin, Dragan
PY  - 2015
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/470
AB  - We propose a method which delivers optimal cubic GaN/AlGaN quantum well profiles such that both the Stark effect and peak intersubband absorption from the ground to the first excited electronic state, in a prescribed range of bias electric fields, are maximized. Our method relies on the Genetic Algorithm which finds globally optimal structures with a predefined number of embedded layers. We investigate simple rectangular quantum wells with embedded step layers for applications in tunable mid-infrared photodetectors. The effects of band nonparabolicity are taken into account to refine our model.
T2  - Optical and Quantum Electronics
T1  - Cubic GaN/AlGaN based quantum wells optimized for applications to tunable mid-infrared photodetectors
VL  - 47
IS  - 4
SP  - 865
EP  - 872
DO  - 10.1007/s11082-014-0016-y
ER  - 

@article{
author = "Radosavljević, Ana and Radovanović, Jelena V. and Milanović, Vitomir B. and Indjin, Dragan",
year = "2015",
abstract = "We propose a method which delivers optimal cubic GaN/AlGaN quantum well profiles such that both the Stark effect and peak intersubband absorption from the ground to the first excited electronic state, in a prescribed range of bias electric fields, are maximized. Our method relies on the Genetic Algorithm which finds globally optimal structures with a predefined number of embedded layers. We investigate simple rectangular quantum wells with embedded step layers for applications in tunable mid-infrared photodetectors. The effects of band nonparabolicity are taken into account to refine our model.",
journal = "Optical and Quantum Electronics",
title = "Cubic GaN/AlGaN based quantum wells optimized for applications to tunable mid-infrared photodetectors",
volume = "47",
number = "4",
pages = "865-872",
doi = "10.1007/s11082-014-0016-y"
}

Radosavljević, A., Radovanović, J. V., Milanović, V. B.,& Indjin, D.. (2015). Cubic GaN/AlGaN based quantum wells optimized for applications to tunable mid-infrared photodetectors. in Optical and Quantum Electronics, 47(4), 865-872.
https://doi.org/10.1007/s11082-014-0016-y

Radosavljević A, Radovanović JV, Milanović VB, Indjin D. Cubic GaN/AlGaN based quantum wells optimized for applications to tunable mid-infrared photodetectors. in Optical and Quantum Electronics. 2015;47(4):865-872.
doi:10.1007/s11082-014-0016-y .

Radosavljević, Ana, Radovanović, Jelena V., Milanović, Vitomir B., Indjin, Dragan, "Cubic GaN/AlGaN based quantum wells optimized for applications to tunable mid-infrared photodetectors" in Optical and Quantum Electronics, 47, no. 4 (2015):865-872,
https://doi.org/10.1007/s11082-014-0016-y . .

TY  - JOUR
AU  - Vuković, Nikola
AU  - Daničić, Aleksandar
AU  - Radovanović, Jelena V.
AU  - Milanović, Vitomir B.
AU  - Indjin, Dragan
PY  - 2015
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/471
AB  - One of the challenges in the design of metamaterials unit cells is the reduction of losses caused by the metallic inclusions. In order to overcome this obstacle, it has been proposed to use the active medium as the unit cell. Quantum cascade lasers are great candidates for the active medium materials since they are able to provide high values of optical gain. In this paper we investigate and compare two quantum cascade structures optimized for emission frequencies lower than 2 THz and simulate the effect of a strong magnetic field applied perpendicularly to the layers. Comprehensive description of conduction-band nonparabolicity is used to calculate the electronic structure, and subsequently evaluate the longitudinal optical phonon and interface roughness scattering rates and solve the system of rate equations which govern the distribution of carriers among the Landau levels. Once we assess the degree of population inversion, we have all the necessary information about the permittivity component along the growth direction of the structure and may determine the conditions under which the structure displays negative refraction.
T2  - Optical and Quantum Electronics
T1  - Possibilities of achieving negative refraction in QCL-based semiconductor metamaterials in the THz spectral range
VL  - 47
IS  - 4
SP  - 883
EP  - 891
DO  - 10.1007/s11082-014-0020-2
ER  - 

@article{
author = "Vuković, Nikola and Daničić, Aleksandar and Radovanović, Jelena V. and Milanović, Vitomir B. and Indjin, Dragan",
year = "2015",
abstract = "One of the challenges in the design of metamaterials unit cells is the reduction of losses caused by the metallic inclusions. In order to overcome this obstacle, it has been proposed to use the active medium as the unit cell. Quantum cascade lasers are great candidates for the active medium materials since they are able to provide high values of optical gain. In this paper we investigate and compare two quantum cascade structures optimized for emission frequencies lower than 2 THz and simulate the effect of a strong magnetic field applied perpendicularly to the layers. Comprehensive description of conduction-band nonparabolicity is used to calculate the electronic structure, and subsequently evaluate the longitudinal optical phonon and interface roughness scattering rates and solve the system of rate equations which govern the distribution of carriers among the Landau levels. Once we assess the degree of population inversion, we have all the necessary information about the permittivity component along the growth direction of the structure and may determine the conditions under which the structure displays negative refraction.",
journal = "Optical and Quantum Electronics",
title = "Possibilities of achieving negative refraction in QCL-based semiconductor metamaterials in the THz spectral range",
volume = "47",
number = "4",
pages = "883-891",
doi = "10.1007/s11082-014-0020-2"
}

Vuković, N., Daničić, A., Radovanović, J. V., Milanović, V. B.,& Indjin, D.. (2015). Possibilities of achieving negative refraction in QCL-based semiconductor metamaterials in the THz spectral range. in Optical and Quantum Electronics, 47(4), 883-891.
https://doi.org/10.1007/s11082-014-0020-2

Vuković N, Daničić A, Radovanović JV, Milanović VB, Indjin D. Possibilities of achieving negative refraction in QCL-based semiconductor metamaterials in the THz spectral range. in Optical and Quantum Electronics. 2015;47(4):883-891.
doi:10.1007/s11082-014-0020-2 .

Vuković, Nikola, Daničić, Aleksandar, Radovanović, Jelena V., Milanović, Vitomir B., Indjin, Dragan, "Possibilities of achieving negative refraction in QCL-based semiconductor metamaterials in the THz spectral range" in Optical and Quantum Electronics, 47, no. 4 (2015):883-891,
https://doi.org/10.1007/s11082-014-0020-2 . .

TY  - CONF
AU  - Vuković, Nikola
AU  - Daničić, Aleksandar
AU  - Radovanović, Jelena
AU  - Milanović, Vitomir
AU  - Boiko, D. L.
PY  - 2015
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/10956
AB  - Quantum Cascade Lasers (QCLs) producing picosecond pulses of high peak power will find numerous novel applications for time-resolved MIR spectroscopy, free space communication, remote atmosphere sensing etc. The short upper state lifetime (~1 ps) in QCLs prohibits passive mode-locking or Q-switched operation because the gain recovers much faster than the pulse repetition rate. Gain switched pulse production has been attempted yielding 120 ps pulse width [1] and active mode-locking was achieved in QCL utilizing diagonal transition [2]. Unfortunately, diagonal transition rendered QCL operation temperature out of the practical use. Experiments reported in [3] evidence that some QCL structures exhibit features of multimode Risken-Nummedal-Graham-Haken (RNGH) instabilities [4,5] at low excess above lasing threshold (pth2<1.1). The onset of such RNGH instabilities and excitation of regular self-pulsations may provide practical means to produce picosecond pulses in the MIR spectral range. Conventional RNGH analysis [4,5] predicts that the second threshold pth2 is in the range of 9 to 16 times above lasing threshold, does not take the spatial grating of population inversion into account and barely agrees with experiments in unidirectional ring fiber lasers [6]. Here we consider Fabry-Perot (FP) cavity QCLs and conventional semiconductor quantum well (QW) LDs. Like in reference [3], we take into account the effect of the induced grating of population inversion, but we also incorporate the grating of the medium polarization and its relaxation due to carrier diffusion. This allows us to explain low second threshold in QCLs without inducing the ambiguous assumption of Ref. [3] of a built-in saturable absorber and Kerr lensing-effect in the waveguide of QCL. We further elucidate the importance of unipolar diffusion in QCLs and ambipolar diffusion in conventional LDs: without diffusion, the second threshold would be too low and independent of the lasing wavelength. Time domain simulations utilizing travelling wave rate equation model of Ref. [7] show irregular self-pulsations, in agreement with experiment in [3]. Shortening of the cavity length down to L=100μm results in the increase of the second threshold up to 2.3-2.5. Above RNGH threshold, steady state regular self-pulsations can be established, preceded by a high-amplitude burst, which might be attributed to Dicke superradiance (SR) [8]. Very high pth2 in conventional LDs is predicted by the model, attributed to ambipolar diffusion. Just like QCLs above the RNGH threshold, FP cavity LDs would exhibit SR emission burst followed by regular RNGH self-pulsations.
PB  - Belgrade : Vinča Institute of Nuclear Sciences
C3  - PHOTONICA2015 : 5th International School and Conference on Photonics and COST actions: MP1204, BM1205 and MP1205 : book of abstracts; August 24-28, 2015; Belgrade
T1  - Multimode RNGH instabilities of Fabry-Perot cavity QCLs: Impact of diffusion
SP  - 115
EP  - 116
UR  - https://hdl.handle.net/21.15107/rcub_vinar_10956
ER  - 

@conference{
author = "Vuković, Nikola and Daničić, Aleksandar and Radovanović, Jelena and Milanović, Vitomir and Boiko, D. L.",
year = "2015",
abstract = "Quantum Cascade Lasers (QCLs) producing picosecond pulses of high peak power will find numerous novel applications for time-resolved MIR spectroscopy, free space communication, remote atmosphere sensing etc. The short upper state lifetime (~1 ps) in QCLs prohibits passive mode-locking or Q-switched operation because the gain recovers much faster than the pulse repetition rate. Gain switched pulse production has been attempted yielding 120 ps pulse width [1] and active mode-locking was achieved in QCL utilizing diagonal transition [2]. Unfortunately, diagonal transition rendered QCL operation temperature out of the practical use. Experiments reported in [3] evidence that some QCL structures exhibit features of multimode Risken-Nummedal-Graham-Haken (RNGH) instabilities [4,5] at low excess above lasing threshold (pth2<1.1). The onset of such RNGH instabilities and excitation of regular self-pulsations may provide practical means to produce picosecond pulses in the MIR spectral range. Conventional RNGH analysis [4,5] predicts that the second threshold pth2 is in the range of 9 to 16 times above lasing threshold, does not take the spatial grating of population inversion into account and barely agrees with experiments in unidirectional ring fiber lasers [6]. Here we consider Fabry-Perot (FP) cavity QCLs and conventional semiconductor quantum well (QW) LDs. Like in reference [3], we take into account the effect of the induced grating of population inversion, but we also incorporate the grating of the medium polarization and its relaxation due to carrier diffusion. This allows us to explain low second threshold in QCLs without inducing the ambiguous assumption of Ref. [3] of a built-in saturable absorber and Kerr lensing-effect in the waveguide of QCL. We further elucidate the importance of unipolar diffusion in QCLs and ambipolar diffusion in conventional LDs: without diffusion, the second threshold would be too low and independent of the lasing wavelength. Time domain simulations utilizing travelling wave rate equation model of Ref. [7] show irregular self-pulsations, in agreement with experiment in [3]. Shortening of the cavity length down to L=100μm results in the increase of the second threshold up to 2.3-2.5. Above RNGH threshold, steady state regular self-pulsations can be established, preceded by a high-amplitude burst, which might be attributed to Dicke superradiance (SR) [8]. Very high pth2 in conventional LDs is predicted by the model, attributed to ambipolar diffusion. Just like QCLs above the RNGH threshold, FP cavity LDs would exhibit SR emission burst followed by regular RNGH self-pulsations.",
publisher = "Belgrade : Vinča Institute of Nuclear Sciences",
journal = "PHOTONICA2015 : 5th International School and Conference on Photonics and COST actions: MP1204, BM1205 and MP1205 : book of abstracts; August 24-28, 2015; Belgrade",
title = "Multimode RNGH instabilities of Fabry-Perot cavity QCLs: Impact of diffusion",
pages = "115-116",
url = "https://hdl.handle.net/21.15107/rcub_vinar_10956"
}

Vuković, N., Daničić, A., Radovanović, J., Milanović, V.,& Boiko, D. L.. (2015). Multimode RNGH instabilities of Fabry-Perot cavity QCLs: Impact of diffusion. in PHOTONICA2015 : 5th International School and Conference on Photonics and COST actions: MP1204, BM1205 and MP1205 : book of abstracts; August 24-28, 2015; Belgrade
Belgrade : Vinča Institute of Nuclear Sciences., 115-116.
https://hdl.handle.net/21.15107/rcub_vinar_10956

Vuković N, Daničić A, Radovanović J, Milanović V, Boiko DL. Multimode RNGH instabilities of Fabry-Perot cavity QCLs: Impact of diffusion. in PHOTONICA2015 : 5th International School and Conference on Photonics and COST actions: MP1204, BM1205 and MP1205 : book of abstracts; August 24-28, 2015; Belgrade. 2015;:115-116.
https://hdl.handle.net/21.15107/rcub_vinar_10956 .

Vuković, Nikola, Daničić, Aleksandar, Radovanović, Jelena, Milanović, Vitomir, Boiko, D. L., "Multimode RNGH instabilities of Fabry-Perot cavity QCLs: Impact of diffusion" in PHOTONICA2015 : 5th International School and Conference on Photonics and COST actions: MP1204, BM1205 and MP1205 : book of abstracts; August 24-28, 2015; Belgrade (2015):115-116,
https://hdl.handle.net/21.15107/rcub_vinar_10956 .

TY  - JOUR
AU  - Radosavljević, Ana
AU  - Radovanović, Jelena V.
AU  - Milanović, Vitomir B.
PY  - 2014
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/5891
AB  - A method is proposed for the optimization of structural parameters of GaN/AlGaN quantum wells and Bragg-confined structures, with respect to peak intersubband absorption from the ground to the first excited electronic state in the mid and near infrared spectral range. It is based on the application of the Genetic Algorithm and delivers globally optimal structures with a preset number of embedded layers. Simple rectangular quantum well profile is investigated for the maximal Stark effect and applications to tunable mid-infrared photodetectors. In case of Bragg-confined structures, an above the barrier bound state is used to extend the range of transition energies above the values available in conventional quantum wells. The effects of band nonparabolicity are taken into account. (C) 2013 Elsevier Ltd. All rights reserved
T2  - Solid State Communications
T1  - Optimization of cubic GaN/AlGaN quantum well-based structures for intersubband absorption in the infrared spectral range
VL  - 182
SP  - 38
EP  - 42
DO  - 10.1016/j.ssc.2013.12.006
ER  - 

@article{
author = "Radosavljević, Ana and Radovanović, Jelena V. and Milanović, Vitomir B.",
year = "2014",
abstract = "A method is proposed for the optimization of structural parameters of GaN/AlGaN quantum wells and Bragg-confined structures, with respect to peak intersubband absorption from the ground to the first excited electronic state in the mid and near infrared spectral range. It is based on the application of the Genetic Algorithm and delivers globally optimal structures with a preset number of embedded layers. Simple rectangular quantum well profile is investigated for the maximal Stark effect and applications to tunable mid-infrared photodetectors. In case of Bragg-confined structures, an above the barrier bound state is used to extend the range of transition energies above the values available in conventional quantum wells. The effects of band nonparabolicity are taken into account. (C) 2013 Elsevier Ltd. All rights reserved",
journal = "Solid State Communications",
title = "Optimization of cubic GaN/AlGaN quantum well-based structures for intersubband absorption in the infrared spectral range",
volume = "182",
pages = "38-42",
doi = "10.1016/j.ssc.2013.12.006"
}

Radosavljević, A., Radovanović, J. V.,& Milanović, V. B.. (2014). Optimization of cubic GaN/AlGaN quantum well-based structures for intersubband absorption in the infrared spectral range. in Solid State Communications, 182, 38-42.
https://doi.org/10.1016/j.ssc.2013.12.006

Radosavljević A, Radovanović JV, Milanović VB. Optimization of cubic GaN/AlGaN quantum well-based structures for intersubband absorption in the infrared spectral range. in Solid State Communications. 2014;182:38-42.
doi:10.1016/j.ssc.2013.12.006 .

Radosavljević, Ana, Radovanović, Jelena V., Milanović, Vitomir B., "Optimization of cubic GaN/AlGaN quantum well-based structures for intersubband absorption in the infrared spectral range" in Solid State Communications, 182 (2014):38-42,
https://doi.org/10.1016/j.ssc.2013.12.006 . .

TY  - JOUR
AU  - Ilic, I.
AU  - Beličev, Petra
AU  - Milanović, Vitomir B.
AU  - Radovanović, Jelena V.
AU  - Hadžievski, Ljupčo
PY  - 2012
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/5135
AB  - The aspects of light propagation through a semiconductor metamaterial (SMM) which consists of two alternating differently doped In0.53Ga0.47As layers are studied analytically and numerically. A general analytical expression for the effective index of refraction of the Poynting vector is derived for periodic structure composed of two alternating layers of absorptive and dispersive semiconductors and light propagation is simulated by finite-difference-time-domain method. Negative values of the effective refractive index with low absorption are observed in the mid-infrared frequency range. The main advantage of this design is the possibility to control the frequency region with negative effective refractive index by changing the doping densities of the layers.
T2  - Journal of Electromagnetic Waves and Applications
T1  - Refractive properties of metamaterial composed of InGaAs layers with alternating doping densities
VL  - 26
IS  - 17-18
SP  - 2323
EP  - 2331
DO  - 10.1080/09205071.2012.733507
ER  - 

@article{
author = "Ilic, I. and Beličev, Petra and Milanović, Vitomir B. and Radovanović, Jelena V. and Hadžievski, Ljupčo",
year = "2012",
abstract = "The aspects of light propagation through a semiconductor metamaterial (SMM) which consists of two alternating differently doped In0.53Ga0.47As layers are studied analytically and numerically. A general analytical expression for the effective index of refraction of the Poynting vector is derived for periodic structure composed of two alternating layers of absorptive and dispersive semiconductors and light propagation is simulated by finite-difference-time-domain method. Negative values of the effective refractive index with low absorption are observed in the mid-infrared frequency range. The main advantage of this design is the possibility to control the frequency region with negative effective refractive index by changing the doping densities of the layers.",
journal = "Journal of Electromagnetic Waves and Applications",
title = "Refractive properties of metamaterial composed of InGaAs layers with alternating doping densities",
volume = "26",
number = "17-18",
pages = "2323-2331",
doi = "10.1080/09205071.2012.733507"
}

Ilic, I., Beličev, P., Milanović, V. B., Radovanović, J. V.,& Hadžievski, L.. (2012). Refractive properties of metamaterial composed of InGaAs layers with alternating doping densities. in Journal of Electromagnetic Waves and Applications, 26(17-18), 2323-2331.
https://doi.org/10.1080/09205071.2012.733507

Ilic I, Beličev P, Milanović VB, Radovanović JV, Hadžievski L. Refractive properties of metamaterial composed of InGaAs layers with alternating doping densities. in Journal of Electromagnetic Waves and Applications. 2012;26(17-18):2323-2331.
doi:10.1080/09205071.2012.733507 .

Ilic, I., Beličev, Petra, Milanović, Vitomir B., Radovanović, Jelena V., Hadžievski, Ljupčo, "Refractive properties of metamaterial composed of InGaAs layers with alternating doping densities" in Journal of Electromagnetic Waves and Applications, 26, no. 17-18 (2012):2323-2331,
https://doi.org/10.1080/09205071.2012.733507 . .

TY  - JOUR
AU  - Radovanović, Jelena V.
AU  - Ramović, Sabina
AU  - Daničić, Aleksandar
AU  - Milanović, Vitomir B.
PY  - 2012
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/5171
AB  - We have considered the realization of metamaterials based on semiconductor quantum nanostructures, in particular, with the structural arrangement as in quantum cascade laser (QCL) designed to achieve optical gain in the mid-infrared and terahertz part of the spectrum. The entire structure is placed in a strong external magnetic field, which facilitates the attainment of sufficient population inversion, necessary to manipulate the permittivity, and enable a left-handed regime.
T2  - Applied Physics. A: Materials Science and Processing
T1  - Negative refraction in semiconductor metamaterials based on quantum cascade laser design for the mid-IR and THz spectral range
VL  - 109
IS  - 4
SP  - 763
EP  - 768
DO  - 10.1007/s00339-012-7343-2
ER  - 

@article{
author = "Radovanović, Jelena V. and Ramović, Sabina and Daničić, Aleksandar and Milanović, Vitomir B.",
year = "2012",
abstract = "We have considered the realization of metamaterials based on semiconductor quantum nanostructures, in particular, with the structural arrangement as in quantum cascade laser (QCL) designed to achieve optical gain in the mid-infrared and terahertz part of the spectrum. The entire structure is placed in a strong external magnetic field, which facilitates the attainment of sufficient population inversion, necessary to manipulate the permittivity, and enable a left-handed regime.",
journal = "Applied Physics. A: Materials Science and Processing",
title = "Negative refraction in semiconductor metamaterials based on quantum cascade laser design for the mid-IR and THz spectral range",
volume = "109",
number = "4",
pages = "763-768",
doi = "10.1007/s00339-012-7343-2"
}

Radovanović, J. V., Ramović, S., Daničić, A.,& Milanović, V. B.. (2012). Negative refraction in semiconductor metamaterials based on quantum cascade laser design for the mid-IR and THz spectral range. in Applied Physics. A: Materials Science and Processing, 109(4), 763-768.
https://doi.org/10.1007/s00339-012-7343-2

Radovanović JV, Ramović S, Daničić A, Milanović VB. Negative refraction in semiconductor metamaterials based on quantum cascade laser design for the mid-IR and THz spectral range. in Applied Physics. A: Materials Science and Processing. 2012;109(4):763-768.
doi:10.1007/s00339-012-7343-2 .

Radovanović, Jelena V., Ramović, Sabina, Daničić, Aleksandar, Milanović, Vitomir B., "Negative refraction in semiconductor metamaterials based on quantum cascade laser design for the mid-IR and THz spectral range" in Applied Physics. A: Materials Science and Processing, 109, no. 4 (2012):763-768,
https://doi.org/10.1007/s00339-012-7343-2 . .

TY  - JOUR
AU  - Radovanović, Jelena V.
AU  - Ilic, Igor
AU  - Beličev, Petra
AU  - Milanović, Vitomir B.
AU  - Hadžievski, Ljupčo
PY  - 2012
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/5172
AB  - We present a comparative analysis of the tunneling times of electromagnetic (EM) waves propagating in isotropic and anisotropic media. First, suitable expressions for the tunneling times in a layered periodic material, with anisotropic properties originating from its structure, are derived, followed by numerical calculations performed for a new type of anisotropic semiconductor metamaterial. In the first case, we have considered a layered structure which contains two differently doped In0.53Ga0.47As semiconductor layers. The second structure under investigation is made of alternately placed layers of doped In0.53Ga0.47As and undoped Al0.48Ga0.52As. The investigation of the dwell time as a function of incident wave frequency has revealed the existence of two peaks, one of which may be interpreted as a consequence of anisotropy, while the other one corresponds to the peak related to the absorption and the group delay. Both of these two peaks are affected by variations of layers doping densities. Furthermore, at increased incident angles of incoming EM waves, the dwell time peak occurs at the upper boundary of the frequency interval, for which the structure exhibits negative refractive index.
T2  - Applied Physics. A: Materials Science and Processing
T1  - Comparison of tunneling times in isotropic and anisotropic media
VL  - 109
IS  - 4
SP  - 997
EP  - 1006
DO  - 10.1007/s00339-012-7393-5
ER  - 

@article{
author = "Radovanović, Jelena V. and Ilic, Igor and Beličev, Petra and Milanović, Vitomir B. and Hadžievski, Ljupčo",
year = "2012",
abstract = "We present a comparative analysis of the tunneling times of electromagnetic (EM) waves propagating in isotropic and anisotropic media. First, suitable expressions for the tunneling times in a layered periodic material, with anisotropic properties originating from its structure, are derived, followed by numerical calculations performed for a new type of anisotropic semiconductor metamaterial. In the first case, we have considered a layered structure which contains two differently doped In0.53Ga0.47As semiconductor layers. The second structure under investigation is made of alternately placed layers of doped In0.53Ga0.47As and undoped Al0.48Ga0.52As. The investigation of the dwell time as a function of incident wave frequency has revealed the existence of two peaks, one of which may be interpreted as a consequence of anisotropy, while the other one corresponds to the peak related to the absorption and the group delay. Both of these two peaks are affected by variations of layers doping densities. Furthermore, at increased incident angles of incoming EM waves, the dwell time peak occurs at the upper boundary of the frequency interval, for which the structure exhibits negative refractive index.",
journal = "Applied Physics. A: Materials Science and Processing",
title = "Comparison of tunneling times in isotropic and anisotropic media",
volume = "109",
number = "4",
pages = "997-1006",
doi = "10.1007/s00339-012-7393-5"
}

Radovanović, J. V., Ilic, I., Beličev, P., Milanović, V. B.,& Hadžievski, L.. (2012). Comparison of tunneling times in isotropic and anisotropic media. in Applied Physics. A: Materials Science and Processing, 109(4), 997-1006.
https://doi.org/10.1007/s00339-012-7393-5

Radovanović JV, Ilic I, Beličev P, Milanović VB, Hadžievski L. Comparison of tunneling times in isotropic and anisotropic media. in Applied Physics. A: Materials Science and Processing. 2012;109(4):997-1006.
doi:10.1007/s00339-012-7393-5 .

Radovanović, Jelena V., Ilic, Igor, Beličev, Petra, Milanović, Vitomir B., Hadžievski, Ljupčo, "Comparison of tunneling times in isotropic and anisotropic media" in Applied Physics. A: Materials Science and Processing, 109, no. 4 (2012):997-1006,
https://doi.org/10.1007/s00339-012-7393-5 . .

TY  - JOUR
AU  - Ilic, I.
AU  - Beličev, Petra
AU  - Milanović, Vitomir B.
PY  - 2012
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/6951
AB  - Tunneling times in an anisotropic structure composed of alternately placed layers of two linear, dispersive and absorptive materials are analyzed in this paper. For such a structure, a general expression for the relation between the two most common tunneling time definitions, namely the dwell time and the group delay, is obtained. Numerical calculations are performed for a new type of semiconductor metamaterial. The results show a peak position frequency mismatch between the dwell time and the group delay, and between the dwell time and the absorption.
T2  - Physica Scripta
T1  - Modeling of tunneling times in anisotropic non-magnetic metamaterials
VL  - T149
DO  - 10.1088/0031-8949/2012/T149/014050
ER  - 

@article{
author = "Ilic, I. and Beličev, Petra and Milanović, Vitomir B.",
year = "2012",
abstract = "Tunneling times in an anisotropic structure composed of alternately placed layers of two linear, dispersive and absorptive materials are analyzed in this paper. For such a structure, a general expression for the relation between the two most common tunneling time definitions, namely the dwell time and the group delay, is obtained. Numerical calculations are performed for a new type of semiconductor metamaterial. The results show a peak position frequency mismatch between the dwell time and the group delay, and between the dwell time and the absorption.",
journal = "Physica Scripta",
title = "Modeling of tunneling times in anisotropic non-magnetic metamaterials",
volume = "T149",
doi = "10.1088/0031-8949/2012/T149/014050"
}

Ilic, I., Beličev, P.,& Milanović, V. B.. (2012). Modeling of tunneling times in anisotropic non-magnetic metamaterials. in Physica Scripta, T149.
https://doi.org/10.1088/0031-8949/2012/T149/014050

Ilic I, Beličev P, Milanović VB. Modeling of tunneling times in anisotropic non-magnetic metamaterials. in Physica Scripta. 2012;T149.
doi:10.1088/0031-8949/2012/T149/014050 .

Ilic, I., Beličev, Petra, Milanović, Vitomir B., "Modeling of tunneling times in anisotropic non-magnetic metamaterials" in Physica Scripta, T149 (2012),
https://doi.org/10.1088/0031-8949/2012/T149/014050 . .

TY  - CONF
AU  - Ilić, Igor
AU  - Beličev, Petra
AU  - Radovanović, Jelena
AU  - Milanović, Vitomir
AU  - Hadžievski, Ljupčo
PY  - 2011
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/10975
PB  - Belgrade : Vinča Institute of Nuclear Sciences
C3  - PHOTONICA2011 : 3rd International School and Conference on Photonics : book of abstracts; August 29- September 2, 2011; Belgrade
T1  - Modeling of tunneling times in anisotropic nonmagnetic metamaterials
SP  - 86
UR  - https://hdl.handle.net/21.15107/rcub_vinar_10975
ER  - 

@conference{
author = "Ilić, Igor and Beličev, Petra and Radovanović, Jelena and Milanović, Vitomir and Hadžievski, Ljupčo",
year = "2011",
publisher = "Belgrade : Vinča Institute of Nuclear Sciences",
journal = "PHOTONICA2011 : 3rd International School and Conference on Photonics : book of abstracts; August 29- September 2, 2011; Belgrade",
title = "Modeling of tunneling times in anisotropic nonmagnetic metamaterials",
pages = "86",
url = "https://hdl.handle.net/21.15107/rcub_vinar_10975"
}

Ilić, I., Beličev, P., Radovanović, J., Milanović, V.,& Hadžievski, L.. (2011). Modeling of tunneling times in anisotropic nonmagnetic metamaterials. in PHOTONICA2011 : 3rd International School and Conference on Photonics : book of abstracts; August 29- September 2, 2011; Belgrade
Belgrade : Vinča Institute of Nuclear Sciences., 86.
https://hdl.handle.net/21.15107/rcub_vinar_10975

Ilić I, Beličev P, Radovanović J, Milanović V, Hadžievski L. Modeling of tunneling times in anisotropic nonmagnetic metamaterials. in PHOTONICA2011 : 3rd International School and Conference on Photonics : book of abstracts; August 29- September 2, 2011; Belgrade. 2011;:86.
https://hdl.handle.net/21.15107/rcub_vinar_10975 .

Ilić, Igor, Beličev, Petra, Radovanović, Jelena, Milanović, Vitomir, Hadžievski, Ljupčo, "Modeling of tunneling times in anisotropic nonmagnetic metamaterials" in PHOTONICA2011 : 3rd International School and Conference on Photonics : book of abstracts; August 29- September 2, 2011; Belgrade (2011):86,
https://hdl.handle.net/21.15107/rcub_vinar_10975 .

TY  - JOUR
AU  - Ilic, I.
AU  - Beličev, Petra
AU  - Milanović, Vitomir B.
AU  - Radovanović, Jelena V.
AU  - Hadžievski, Ljupčo
PY  - 2011
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/4242
AB  - We present an analysis of the influence of the Goos-Hanchen effect on tunneling times, group delay and dwell time, of electromagnetic waves propagating through an obstacle made of left-handed metamaterial embedded in a dielectric which exhibits saturable type of nonlinearity. The derived equations show that only the group delay, is affected by the Goos-Hanchen shift without any impact on the dwell time. Besides the reduction of the group delay, the most remarkable result is the possibility for total reduction of the Goos-Hanchen shift for finite incident angles. These phenomena are observable in the frequency region for which metamaterial exhibits negative index of refraction. (C) 2011 Elsevier B.V. All rights reserved.
T2  - Physics Letters A
T1  - Goos-Hanchen shift and time delay in dispersive nonlinear media
VL  - 375
IS  - 10
SP  - 1357
EP  - 1361
DO  - 10.1016/j.physleta.2011.01.053
ER  - 

@article{
author = "Ilic, I. and Beličev, Petra and Milanović, Vitomir B. and Radovanović, Jelena V. and Hadžievski, Ljupčo",
year = "2011",
abstract = "We present an analysis of the influence of the Goos-Hanchen effect on tunneling times, group delay and dwell time, of electromagnetic waves propagating through an obstacle made of left-handed metamaterial embedded in a dielectric which exhibits saturable type of nonlinearity. The derived equations show that only the group delay, is affected by the Goos-Hanchen shift without any impact on the dwell time. Besides the reduction of the group delay, the most remarkable result is the possibility for total reduction of the Goos-Hanchen shift for finite incident angles. These phenomena are observable in the frequency region for which metamaterial exhibits negative index of refraction. (C) 2011 Elsevier B.V. All rights reserved.",
journal = "Physics Letters A",
title = "Goos-Hanchen shift and time delay in dispersive nonlinear media",
volume = "375",
number = "10",
pages = "1357-1361",
doi = "10.1016/j.physleta.2011.01.053"
}

Ilic, I., Beličev, P., Milanović, V. B., Radovanović, J. V.,& Hadžievski, L.. (2011). Goos-Hanchen shift and time delay in dispersive nonlinear media. in Physics Letters A, 375(10), 1357-1361.
https://doi.org/10.1016/j.physleta.2011.01.053

Ilic I, Beličev P, Milanović VB, Radovanović JV, Hadžievski L. Goos-Hanchen shift and time delay in dispersive nonlinear media. in Physics Letters A. 2011;375(10):1357-1361.
doi:10.1016/j.physleta.2011.01.053 .

Ilic, I., Beličev, Petra, Milanović, Vitomir B., Radovanović, Jelena V., Hadžievski, Ljupčo, "Goos-Hanchen shift and time delay in dispersive nonlinear media" in Physics Letters A, 375, no. 10 (2011):1357-1361,
https://doi.org/10.1016/j.physleta.2011.01.053 . .

TY  - JOUR
AU  - Radovanović, Jelena V.
AU  - Danici, A.
AU  - Milanović, Vitomir B.
AU  - Indjin, Dragan
AU  - Ikonić, Zoran
PY  - 2011
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/6915
AB  - We present a detailed analysis of GaAs/AlGaAs terahertz quantum cascade laser in the presence of an intense external magnetic field. One of the objectives in further development of THz quantum cascade laser is the realization of structures operating at higher temperatures. This is difficult to obtain as the operating photon emission energy is smaller than the longitudinal-optical phonon energy in the semiconductor material. With increased temperature, electrons in the upper radiative state gain sufficient in-plane energy to emit an longitudinal-optical phonon, which represents a non-radiative scattering and reduces the optical gain. By applying strong magnetic field, two-dimensional continuous energy subbands become split into series of discrete Landau levels, and at particular values of B it is possible to quench these non-radiative channels. Numerical simulations are performed on two-well design quantum cascade laser operating at 4.6 THz, implemented in CaAs/Al(0.15)Ga(0.85)As, and the magnetic field is perpendicular to the epitaxial layers. Strong oscillations of carrier lifetimes for the upper state of the laser transition, as a function of magnetic field are observed, which can be attributed to interface roughness scattering and longitudinal-optical phonon scattering between Landau levels.
T2  - Acta Physica Polonica A
T1  - Inter-Landau Level Scattering Processes in Magnetic Field Assisted THz Quantum Cascade Laser
VL  - 120
IS  - 2
SP  - 227
EP  - 230
DO  - 10.12693/APhysPolA.120.227
ER  - 

@article{
author = "Radovanović, Jelena V. and Danici, A. and Milanović, Vitomir B. and Indjin, Dragan and Ikonić, Zoran",
year = "2011",
abstract = "We present a detailed analysis of GaAs/AlGaAs terahertz quantum cascade laser in the presence of an intense external magnetic field. One of the objectives in further development of THz quantum cascade laser is the realization of structures operating at higher temperatures. This is difficult to obtain as the operating photon emission energy is smaller than the longitudinal-optical phonon energy in the semiconductor material. With increased temperature, electrons in the upper radiative state gain sufficient in-plane energy to emit an longitudinal-optical phonon, which represents a non-radiative scattering and reduces the optical gain. By applying strong magnetic field, two-dimensional continuous energy subbands become split into series of discrete Landau levels, and at particular values of B it is possible to quench these non-radiative channels. Numerical simulations are performed on two-well design quantum cascade laser operating at 4.6 THz, implemented in CaAs/Al(0.15)Ga(0.85)As, and the magnetic field is perpendicular to the epitaxial layers. Strong oscillations of carrier lifetimes for the upper state of the laser transition, as a function of magnetic field are observed, which can be attributed to interface roughness scattering and longitudinal-optical phonon scattering between Landau levels.",
journal = "Acta Physica Polonica A",
title = "Inter-Landau Level Scattering Processes in Magnetic Field Assisted THz Quantum Cascade Laser",
volume = "120",
number = "2",
pages = "227-230",
doi = "10.12693/APhysPolA.120.227"
}

Radovanović, J. V., Danici, A., Milanović, V. B., Indjin, D.,& Ikonić, Z.. (2011). Inter-Landau Level Scattering Processes in Magnetic Field Assisted THz Quantum Cascade Laser. in Acta Physica Polonica A, 120(2), 227-230.
https://doi.org/10.12693/APhysPolA.120.227

Radovanović JV, Danici A, Milanović VB, Indjin D, Ikonić Z. Inter-Landau Level Scattering Processes in Magnetic Field Assisted THz Quantum Cascade Laser. in Acta Physica Polonica A. 2011;120(2):227-230.
doi:10.12693/APhysPolA.120.227 .

Radovanović, Jelena V., Danici, A., Milanović, Vitomir B., Indjin, Dragan, Ikonić, Zoran, "Inter-Landau Level Scattering Processes in Magnetic Field Assisted THz Quantum Cascade Laser" in Acta Physica Polonica A, 120, no. 2 (2011):227-230,
https://doi.org/10.12693/APhysPolA.120.227 . .

TY  - JOUR
AU  - Radovanovic, Jelena V.
AU  - Ilic, Igor
AU  - Beličev, Petra
AU  - Hadžievski, Ljupčo
AU  - Milanović, Vitomir B.
PY  - 2011
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/4312
AB  - Investigating the propagation of electromagnetic radiation in linear and nonlinear materials (with third-order nonlinearity), we derived a general expression for the dwell time valid for all linear media, as well as its relation with the group delay. The obtained results indicate that, for a nonmagnetic lossless material, the group delay reduces to the sum of the dwell time and the self-interference time. Calculations confirmed the occurrence of the Hartman effect in negative-refractive-index metamaterials (the dwell time saturates with increasing obstacle length), as well as the negative group delay in a certain spectral regime. Analysis of the Goos-Hanchen shift, in case of an obstacle made of negative-refractive-index metamaterial embedded in a dielectric with saturable nonlinearity, showed that there is no impact on the dwell time, while various effects on the group delay may be achieved, including its reduction or even preservation for nonzero incident angles. (C) 2011 Society of Photo-Optical Instrumentation Engineers (SPIE). [DOI: 10.1117/1.3586782]
T2  - Journal of Nanophotonics
T1  - Tunneling times in dispersive and third-order nonlinear optical metamaterials
VL  - 5
DO  - 10.1117/1.3586782
ER  - 

@article{
author = "Radovanovic, Jelena V. and Ilic, Igor and Beličev, Petra and Hadžievski, Ljupčo and Milanović, Vitomir B.",
year = "2011",
abstract = "Investigating the propagation of electromagnetic radiation in linear and nonlinear materials (with third-order nonlinearity), we derived a general expression for the dwell time valid for all linear media, as well as its relation with the group delay. The obtained results indicate that, for a nonmagnetic lossless material, the group delay reduces to the sum of the dwell time and the self-interference time. Calculations confirmed the occurrence of the Hartman effect in negative-refractive-index metamaterials (the dwell time saturates with increasing obstacle length), as well as the negative group delay in a certain spectral regime. Analysis of the Goos-Hanchen shift, in case of an obstacle made of negative-refractive-index metamaterial embedded in a dielectric with saturable nonlinearity, showed that there is no impact on the dwell time, while various effects on the group delay may be achieved, including its reduction or even preservation for nonzero incident angles. (C) 2011 Society of Photo-Optical Instrumentation Engineers (SPIE). [DOI: 10.1117/1.3586782]",
journal = "Journal of Nanophotonics",
title = "Tunneling times in dispersive and third-order nonlinear optical metamaterials",
volume = "5",
doi = "10.1117/1.3586782"
}

Radovanovic, J. V., Ilic, I., Beličev, P., Hadžievski, L.,& Milanović, V. B.. (2011). Tunneling times in dispersive and third-order nonlinear optical metamaterials. in Journal of Nanophotonics, 5.
https://doi.org/10.1117/1.3586782

Radovanovic JV, Ilic I, Beličev P, Hadžievski L, Milanović VB. Tunneling times in dispersive and third-order nonlinear optical metamaterials. in Journal of Nanophotonics. 2011;5.
doi:10.1117/1.3586782 .

Radovanovic, Jelena V., Ilic, Igor, Beličev, Petra, Hadžievski, Ljupčo, Milanović, Vitomir B., "Tunneling times in dispersive and third-order nonlinear optical metamaterials" in Journal of Nanophotonics, 5 (2011),
https://doi.org/10.1117/1.3586782 . .

TY  - JOUR
AU  - Daničić, Aleksandar
AU  - Radovanović, Jelena V.
AU  - Milanović, Vitomir B.
AU  - Indjin, Dragan
AU  - Ikonić, Zoran
PY  - 2010
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/3874
AB  - We explore the possibilities of using advanced tools for global optimization, namely the genetic algorithm, to obtain structural parameters of gain-maximized quantum cascade laser (QCL) emitting at specified wavelengths, suitable for detection of pollutant gasses, such as SO(2), HNO(3), CH(4) and NH(3), in the ambient air. Upon completing this initial optimization stage, we introduce a strong external magnetic field perpendicular to the epitaxial layers, to fine tune the laser output properties. This magnetic field alters the electron energy spectrum by splitting the continuous energy subbands into discrete Landau levels whose arrangement influences the magnitude of the optical gain. In addition, strong effects of band nonparabolicity result in subtle changes in the lasing wavelength at magnetic fields which maximize the gain, thus allowing us to explore the prospects of multi-wavelength emission of the given structure, and achieving resonance with additional compounds, absorbing at wavelengths close to the original one. Numerical results are presented for GaAs/Al(x)Ga(1-x) As based QCL structures designed for operation in the mid-infrared part of the spectrum.
T2  - Journal of Physics. D: Applied Physics
T1  - Optimization and magnetic-field tunability of quantum cascade laser for applications in trace gas detection and monitoring
VL  - 43
IS  - 4
DO  - 10.1088/0022-3727/43/4/045101
ER  - 

@article{
author = "Daničić, Aleksandar and Radovanović, Jelena V. and Milanović, Vitomir B. and Indjin, Dragan and Ikonić, Zoran",
year = "2010",
abstract = "We explore the possibilities of using advanced tools for global optimization, namely the genetic algorithm, to obtain structural parameters of gain-maximized quantum cascade laser (QCL) emitting at specified wavelengths, suitable for detection of pollutant gasses, such as SO(2), HNO(3), CH(4) and NH(3), in the ambient air. Upon completing this initial optimization stage, we introduce a strong external magnetic field perpendicular to the epitaxial layers, to fine tune the laser output properties. This magnetic field alters the electron energy spectrum by splitting the continuous energy subbands into discrete Landau levels whose arrangement influences the magnitude of the optical gain. In addition, strong effects of band nonparabolicity result in subtle changes in the lasing wavelength at magnetic fields which maximize the gain, thus allowing us to explore the prospects of multi-wavelength emission of the given structure, and achieving resonance with additional compounds, absorbing at wavelengths close to the original one. Numerical results are presented for GaAs/Al(x)Ga(1-x) As based QCL structures designed for operation in the mid-infrared part of the spectrum.",
journal = "Journal of Physics. D: Applied Physics",
title = "Optimization and magnetic-field tunability of quantum cascade laser for applications in trace gas detection and monitoring",
volume = "43",
number = "4",
doi = "10.1088/0022-3727/43/4/045101"
}

Daničić, A., Radovanović, J. V., Milanović, V. B., Indjin, D.,& Ikonić, Z.. (2010). Optimization and magnetic-field tunability of quantum cascade laser for applications in trace gas detection and monitoring. in Journal of Physics. D: Applied Physics, 43(4).
https://doi.org/10.1088/0022-3727/43/4/045101

Daničić A, Radovanović JV, Milanović VB, Indjin D, Ikonić Z. Optimization and magnetic-field tunability of quantum cascade laser for applications in trace gas detection and monitoring. in Journal of Physics. D: Applied Physics. 2010;43(4).
doi:10.1088/0022-3727/43/4/045101 .

Daničić, Aleksandar, Radovanović, Jelena V., Milanović, Vitomir B., Indjin, Dragan, Ikonić, Zoran, "Optimization and magnetic-field tunability of quantum cascade laser for applications in trace gas detection and monitoring" in Journal of Physics. D: Applied Physics, 43, no. 4 (2010),
https://doi.org/10.1088/0022-3727/43/4/045101 . .

TY  - JOUR
AU  - Daničić, Aleksandar
AU  - Radovanović, Jelena V.
AU  - Milanović, Vitomir B.
AU  - Indjin, Dragan
AU  - Ikonić, Zoran
PY  - 2010
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/6870
AB  - We present a method for systematic optimization of quantum cascade laser active region, based on the use of the genetic algorithm. The method aims at obtaining a gain-maximized structure, designed to emit radiation at specified wavelengths suitable for direct absorption by pollutant gasses present in the ambient air. After the initial optimization stage, we introduce a strong external magnetic field to tune the laser output properties and to slightly modify the emission wavelength to match the absorption lines of additional compounds. The magnetic field is applied perpendicularly to the epitaxial layers, thus causing two dimensional continuous energy subbands to split into series of discrete Landau levels. This affects all the relevant relaxation processes in the structure and consequently the lifetime of carriers in the upper laser level. Furthermore, strong effects of band nonparabolicity result in subtle changes of the lasing wavelength at magnetic fields which maximize the gain, thus providing a path for fine tuning of the output radiation properties. Numerical results are presented for GaAs/Al(x)Ga(1-x)As based quantum cascade laser structures designed to emit at particular wavelengths in the mid infrared part of the spectrum.
T2  - Acta Physica Polonica A
T1  - Quantum Cascade Laser Design for Tunable Output at Characteristic Wavelengths in the Mid-Infrared Spectral Range
VL  - 117
IS  - 5
SP  - 772
EP  - 776
DO  - 10.12693/APhysPolA.117.772
ER  - 

@article{
author = "Daničić, Aleksandar and Radovanović, Jelena V. and Milanović, Vitomir B. and Indjin, Dragan and Ikonić, Zoran",
year = "2010",
abstract = "We present a method for systematic optimization of quantum cascade laser active region, based on the use of the genetic algorithm. The method aims at obtaining a gain-maximized structure, designed to emit radiation at specified wavelengths suitable for direct absorption by pollutant gasses present in the ambient air. After the initial optimization stage, we introduce a strong external magnetic field to tune the laser output properties and to slightly modify the emission wavelength to match the absorption lines of additional compounds. The magnetic field is applied perpendicularly to the epitaxial layers, thus causing two dimensional continuous energy subbands to split into series of discrete Landau levels. This affects all the relevant relaxation processes in the structure and consequently the lifetime of carriers in the upper laser level. Furthermore, strong effects of band nonparabolicity result in subtle changes of the lasing wavelength at magnetic fields which maximize the gain, thus providing a path for fine tuning of the output radiation properties. Numerical results are presented for GaAs/Al(x)Ga(1-x)As based quantum cascade laser structures designed to emit at particular wavelengths in the mid infrared part of the spectrum.",
journal = "Acta Physica Polonica A",
title = "Quantum Cascade Laser Design for Tunable Output at Characteristic Wavelengths in the Mid-Infrared Spectral Range",
volume = "117",
number = "5",
pages = "772-776",
doi = "10.12693/APhysPolA.117.772"
}

Daničić, A., Radovanović, J. V., Milanović, V. B., Indjin, D.,& Ikonić, Z.. (2010). Quantum Cascade Laser Design for Tunable Output at Characteristic Wavelengths in the Mid-Infrared Spectral Range. in Acta Physica Polonica A, 117(5), 772-776.
https://doi.org/10.12693/APhysPolA.117.772

Daničić A, Radovanović JV, Milanović VB, Indjin D, Ikonić Z. Quantum Cascade Laser Design for Tunable Output at Characteristic Wavelengths in the Mid-Infrared Spectral Range. in Acta Physica Polonica A. 2010;117(5):772-776.
doi:10.12693/APhysPolA.117.772 .

Daničić, Aleksandar, Radovanović, Jelena V., Milanović, Vitomir B., Indjin, Dragan, Ikonić, Zoran, "Quantum Cascade Laser Design for Tunable Output at Characteristic Wavelengths in the Mid-Infrared Spectral Range" in Acta Physica Polonica A, 117, no. 5 (2010):772-776,
https://doi.org/10.12693/APhysPolA.117.772 . .

TY  - JOUR
AU  - Beličev, Petra
AU  - Ilic, Igor
AU  - Milanović, Vitomir B.
AU  - Radovanović, Jelena V.
AU  - Hadžievski, Ljupčo
PY  - 2009
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/3781
AB  - Tunneling times of electromagnetic planar wave propagating through a barrier made of split-ring resonators and long metallic wires embedded into a dielectric with saturable nonlinearity are analyzed. For such structure, analytical expressions for the tunneling times and relation between the group delay and the dwell time are obtained. The electric-field distribution inside the barrier is numerically evaluated and a detailed study of the influence of nonlinearity on the spectral structures of the tunneling times is performed. It is demonstrated that intensity variation in the incident field may change the wave propagation direction, the sign of the barriers refractive index, and group delay.
T2  - Physical Review A
T1  - Tunneling times in metamaterials with saturable nonlinearity
VL  - 80
IS  - 2
DO  - 10.1103/PhysRevA.80.023821
ER  - 

@article{
author = "Beličev, Petra and Ilic, Igor and Milanović, Vitomir B. and Radovanović, Jelena V. and Hadžievski, Ljupčo",
year = "2009",
abstract = "Tunneling times of electromagnetic planar wave propagating through a barrier made of split-ring resonators and long metallic wires embedded into a dielectric with saturable nonlinearity are analyzed. For such structure, analytical expressions for the tunneling times and relation between the group delay and the dwell time are obtained. The electric-field distribution inside the barrier is numerically evaluated and a detailed study of the influence of nonlinearity on the spectral structures of the tunneling times is performed. It is demonstrated that intensity variation in the incident field may change the wave propagation direction, the sign of the barriers refractive index, and group delay.",
journal = "Physical Review A",
title = "Tunneling times in metamaterials with saturable nonlinearity",
volume = "80",
number = "2",
doi = "10.1103/PhysRevA.80.023821"
}

Beličev, P., Ilic, I., Milanović, V. B., Radovanović, J. V.,& Hadžievski, L.. (2009). Tunneling times in metamaterials with saturable nonlinearity. in Physical Review A, 80(2).
https://doi.org/10.1103/PhysRevA.80.023821

Beličev P, Ilic I, Milanović VB, Radovanović JV, Hadžievski L. Tunneling times in metamaterials with saturable nonlinearity. in Physical Review A. 2009;80(2).
doi:10.1103/PhysRevA.80.023821 .

Beličev, Petra, Ilic, Igor, Milanović, Vitomir B., Radovanović, Jelena V., Hadžievski, Ljupčo, "Tunneling times in metamaterials with saturable nonlinearity" in Physical Review A, 80, no. 2 (2009),
https://doi.org/10.1103/PhysRevA.80.023821 . .

TY  - JOUR
AU  - Beličev, Petra
AU  - Ilic, I.
AU  - Radovanović, Jelena V.
AU  - Milanović, Vitomir B.
AU  - Hadžievski, Ljupčo
PY  - 2009
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/6799
AB  - Time delays for an intense transverse electric wave propagating through a slab with saturable nonlinearity are investigated. The nonlinearity is assumed in a form of the Vinetskii-Kukhtarev model, which is relevant for the slabs made of nonlinear photorefractive crystals, such as GaAs and LiNbO(3), which feature a saturable nonlinearity. The expressions for the group delay and the dwell time are derived and the relation between them is studied. It is shown that the difference between them has three different contributions. The first one corresponds to the self-interference associated with the dispersion of the medium surrounding the slab. The other two appear due to the nonlinearity of the slab and oblique incidence of the transverse electric wave. All the results are compared with the case of dielectric slabs with cubic (Kerr) nonlinearity.
T2  - Acta Physica Polonica A
T1  - Time Delay in Thin Dielectric Slabs with Saturable Nonlinearity
VL  - 115
IS  - 4
SP  - 834
EP  - 837
DO  - 10.12693/APhysPolA.115.834
ER  - 

@article{
author = "Beličev, Petra and Ilic, I. and Radovanović, Jelena V. and Milanović, Vitomir B. and Hadžievski, Ljupčo",
year = "2009",
abstract = "Time delays for an intense transverse electric wave propagating through a slab with saturable nonlinearity are investigated. The nonlinearity is assumed in a form of the Vinetskii-Kukhtarev model, which is relevant for the slabs made of nonlinear photorefractive crystals, such as GaAs and LiNbO(3), which feature a saturable nonlinearity. The expressions for the group delay and the dwell time are derived and the relation between them is studied. It is shown that the difference between them has three different contributions. The first one corresponds to the self-interference associated with the dispersion of the medium surrounding the slab. The other two appear due to the nonlinearity of the slab and oblique incidence of the transverse electric wave. All the results are compared with the case of dielectric slabs with cubic (Kerr) nonlinearity.",
journal = "Acta Physica Polonica A",
title = "Time Delay in Thin Dielectric Slabs with Saturable Nonlinearity",
volume = "115",
number = "4",
pages = "834-837",
doi = "10.12693/APhysPolA.115.834"
}

Beličev, P., Ilic, I., Radovanović, J. V., Milanović, V. B.,& Hadžievski, L.. (2009). Time Delay in Thin Dielectric Slabs with Saturable Nonlinearity. in Acta Physica Polonica A, 115(4), 834-837.
https://doi.org/10.12693/APhysPolA.115.834

Beličev P, Ilic I, Radovanović JV, Milanović VB, Hadžievski L. Time Delay in Thin Dielectric Slabs with Saturable Nonlinearity. in Acta Physica Polonica A. 2009;115(4):834-837.
doi:10.12693/APhysPolA.115.834 .

Beličev, Petra, Ilic, I., Radovanović, Jelena V., Milanović, Vitomir B., Hadžievski, Ljupčo, "Time Delay in Thin Dielectric Slabs with Saturable Nonlinearity" in Acta Physica Polonica A, 115, no. 4 (2009):834-837,
https://doi.org/10.12693/APhysPolA.115.834 . .

TY  - JOUR
AU  - Ilic, I.
AU  - Beličev, Petra
AU  - Milanović, Vitomir B.
AU  - Radovanović, Jelena V.
PY  - 2009
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/6836
AB  - In this paper, a more general expression that describes the relationship between dwell time and group delay is derived. This expression is valid for all kinds of materials, including negative-index metamaterials (NIMs). An obstacle made of double-negative NIMs (DN-NIMs) and surrounded by a double-positive waveguide was used as a model. In the cases where the obstacle was made of left-handed materials and the surroundings were air, it has been shown that the dwell time and absorption have similar dependences on the incident wave frequency. On the other hand, group delay becomes negative in some cases. Numerical results show that an increase in the length of the obstacle leads to saturation of the dwell time and absorption, which is in accordance with the phenomenon known as the Hartman effect. Similar results were obtained for terahertz range of frequencies and for the dispersive waveguide. In this case, it is shown that there is a certain range of frequencies where group velocity is positive, whereas the phase velocity remains negative, i.e. the peak of the output pulse appears before the peak of the input pulse. Finally, the use of a model that considers an obstacle made of a lossless, non-magnetic metamaterial, with background permittivity equal to 1 and a dispersive waveguide, leads to the appearance of a new delay, called self-interference time.
T2  - Physica Scripta
T1  - Modeling of dwell time and group delay in dispersive and absorptive media
VL  - T135
DO  - 10.1088/0031-8949/2009/T135/014040
ER  - 

@article{
author = "Ilic, I. and Beličev, Petra and Milanović, Vitomir B. and Radovanović, Jelena V.",
year = "2009",
abstract = "In this paper, a more general expression that describes the relationship between dwell time and group delay is derived. This expression is valid for all kinds of materials, including negative-index metamaterials (NIMs). An obstacle made of double-negative NIMs (DN-NIMs) and surrounded by a double-positive waveguide was used as a model. In the cases where the obstacle was made of left-handed materials and the surroundings were air, it has been shown that the dwell time and absorption have similar dependences on the incident wave frequency. On the other hand, group delay becomes negative in some cases. Numerical results show that an increase in the length of the obstacle leads to saturation of the dwell time and absorption, which is in accordance with the phenomenon known as the Hartman effect. Similar results were obtained for terahertz range of frequencies and for the dispersive waveguide. In this case, it is shown that there is a certain range of frequencies where group velocity is positive, whereas the phase velocity remains negative, i.e. the peak of the output pulse appears before the peak of the input pulse. Finally, the use of a model that considers an obstacle made of a lossless, non-magnetic metamaterial, with background permittivity equal to 1 and a dispersive waveguide, leads to the appearance of a new delay, called self-interference time.",
journal = "Physica Scripta",
title = "Modeling of dwell time and group delay in dispersive and absorptive media",
volume = "T135",
doi = "10.1088/0031-8949/2009/T135/014040"
}

Ilic, I., Beličev, P., Milanović, V. B.,& Radovanović, J. V.. (2009). Modeling of dwell time and group delay in dispersive and absorptive media. in Physica Scripta, T135.
https://doi.org/10.1088/0031-8949/2009/T135/014040

Ilic I, Beličev P, Milanović VB, Radovanović JV. Modeling of dwell time and group delay in dispersive and absorptive media. in Physica Scripta. 2009;T135.
doi:10.1088/0031-8949/2009/T135/014040 .

Ilic, I., Beličev, Petra, Milanović, Vitomir B., Radovanović, Jelena V., "Modeling of dwell time and group delay in dispersive and absorptive media" in Physica Scripta, T135 (2009),
https://doi.org/10.1088/0031-8949/2009/T135/014040 . .