Influence of a resonance on delay times in terahertz chiral metamaterial slab

Abstract

The advantage of metamaterials made of resonant particles is that, in the interaction with THz waves, they can generate enhanced response which enables diverse functionalities in THz frequency range. In view of that, it was pointed out that the control of delay times of THz pulses can be used for a variety of THz applications [1, 2]. On the other hand, during the interaction with light, chiral metamaterials exhibit optical activity andcircular dichroism as a consequence of different propagation of right (RCP) and left (LCP) circularly polarised waves [3]. Here, we consider the delay times that characterize the interaction of THz wave with a chiral metamaterial slab consisting of resonant omega (Ω)particles embedded in dielectric material. We observe the interaction of RCP and LCP waves with the slab and focus on the analysis of various effects that occur due to the different polarisation of incident waves. It follows that the RCP wave has much stronger coupling with the resonant particles than the LCP wave. Results show that the energy density, absorption and hence, the dwell time of RCP wave have higher values at the resonant frequency comparing to the case when LCP wave interacts with the slab. Calculations were done performing numerical simulations of the resonant Ω particles, as well as by using the effective parameters extracted through parameter retrieval procedure considering a homogenous chiral slab. To the best of our knowledge, this is the first analysis of delay times in chiral metamaterial [4] and obtained results can be used for circular polarisation characterization in THz spectral region. Additionally, we analyse the impact of incident field intensity on delay times for the case of homogenous nonlinear chiral slab presuming that the chiral particles are immersed in nonlinear dielectric of Kerr type. Due to the presence of nonlinearity, common features of metamaterials can be significantly altered [5]. We present our analyses on the nonlinear effects related to resonant behaviour of circularly polarised waves which will affect the corresponding delay times.