@conference{
author = "Daničić, Aleksandar and Vuković, N. and Radovanović, J. and Milanović, V.",
year = "2015",
abstract = "The rapidly emerging field of nano-optoelectronics is based on the understanding and control of intersubband transitions in nano-dimensional systems. One of the most striking outcomes of intersubband transitions engineering is the quantum cascade laser (QCL) – an efficient and reliable unipolar semiconductor laser source [1], with the possibility to operate from the mid-infrared (MIR) to the THz range of frequencies. These powerful devices are particularly appreciated for such wide scope of operating wavelengths which can be achieved by using the same heterostructure combination, but changing the design of the active region, i.e. ‘tailoring’ the layers’ widths and composition. This renders QCLs suitable for numerous applications, including free-space communications, medical diagnostics and in particular, chemical sensing and monitoring [2]. In the MIR part of the spectrum, QCLs are of great interest for gas sensing and monitoring. We explore the possibilities of using advanced tools for global optimization, namely the genetic algorithm, to obtain structural parameters of gain-maximized QCL emitting at specified wavelengths, suitable for detection of pollutant gasses, such as SO2, HNO3, CH4 and NH3, in the ambient air. Then we introduce a strong external magnetic field perpendicular to the epitaxial layers, to fine tune the laser output properties [2]. 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. THz frequencies belong to the quite under-utilized part of the electromagnetic spectrum, despite their significant application potential. This is mostly due to the lack of coherent solid-state THz sources. The so called „THz gap“ falls between two frequency ranges that have been well developed, the microwave and millimeter-wave frequency range. THz QCLs are great candidates to fill in this gap [3]. We have analyzed two structures lasing in this region (both of them reported in the literature, but not studied under the influence of an external magnetic field), the three- and four-well (per period) based structures that operate at 3.9THz and 1.9THz, respectively, 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 carefully accounted for. Because of their high output gain, QCLs are suitable to be used as active media in metamaterial unit cells, thus enabling evasion of metallic inclusions present in conventional metamaterials [4]. We analyze a quantum cascade structure lasing at 4.6THz, placed under the influence of a strong magnetic field. We first solve the full system of rate equations for all the relevant Landau levels, and obtain the necessary information about the carrier distribution among the levels, after which we are able to evaluate the permittivity component along the growth direction 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 = "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 = "Modeling and applications of Quantum Cascade in external magnetic field",
pages = "38-39",
url = "https://hdl.handle.net/21.15107/rcub_vinar_12002"
}
