Bi-modal resonance and spectral characteristics of a thin chiral slab resonator on an achiral substrate using Fresnel coefficients

Abstract

Recently, some work involving investigation of polarization states and Fresnel coefficients (FCs) at an achiral/chiral (ACC) interface indicated that depending on specific chiral bands and also the density (or phase index) of the two dielectrics, certain types of anomalous behavior would result. These anomalies included Brewster effects for s-polarized incident light, and total internal reflection (TIR) for propagation from lower to higher phase index. Analog time signals as well as 2-dimensional stationary images were propagated across the ACC boundary to determine the effect of chirality and parameters such as permittivity and permeability under dispersion.1-3 Extensions to the case of two interfaces comprised of an ACC on the front end and a chiral/achiral (CAC) on the back will be considered in this work. We note that a slab resonator is amenable to analyses similar to a Fabry-Perot (FP) resonator. Analysis is carried out here for the chiral slab (say with thickness d) having both ACC and CAC boundaries; here multiple reflections and transmissions are expected. Matlab simulations are carried out by incorporating boundary conditions and deriving the effective transmitted and reflected fields relative to the slab. The results are examined for a thin chiral slab with thickness d (sandwiched between achiral surface and substrate layers) in the range 10-100 nm. The transmission characteristics (which are examined to study the resonance behavior of a typical FP etalon) are investigated as functions of wavelength or frequency in the thick and thin film limits, and results are compared from resonance, resolution and polarization perspectives.