Amplification in 1D photonic multilayer structure with spatially chirped PT-symmetric defect in Terahertz domain

Abstract

In this paper, we study nonreciprocal enhanced amplification of optical characteristics of a one-dimensional (1D) photonic multilayer structure with a parity-time (PT) symmetric defect layer in the Terahertz regime. Non-Hermitian scattering properties of the 1D photonic structure with different spatially chirped defect layers are explained using the transfer matrix method (TMM) and scattering matrix. The proposed 1D photonic structure exhibits enhanced non-reciprocal reflection with constant loss and gain in the defect layer. In contrast, periodic modulations in loss and gain lead to unidirectional amplification of discrete defect mode. The considered 1D structure is also investigated with the variation in incident angle, which shows the shift of certain defect modes towards higher frequencies and the conversion of perfect absorption points to lasing points for forward and backward incidences. In addition, different chirped profiles of loss and gain modulate the defect modes significantly and induce amplification at a particular incident angle and loss/gain value. The observed amplifications of defect modes can enact unidirectional as well as bidirectional lasing action with proper choice of the chirp profile of gain and loss in the defect layer.