Pt-symmetric transverse mode splitting in coupled quantum cascade lasers

Abstract

Separation of transverse modes in waveguides typically achieved by manipulating mode effective indices is of current interest in integrated optics and various designs have been proposed. Recently, implementation of non-Hermitian optics under parity time (PT) symmetry has led to an alternate class of devices employing gain and loss media with far reaching results. Introduction of PT symmetry to non-Hermitian systems results in real solutions while symmetry breaking results in imaginary eigenvalues. However, applications of PT symmetry in the infrared devices is quite limited. In this work, we demonstrate a mode splitter that can separate transverse modes in coupled PT symmetric in realistic quantum cascade lasers (QC lasers). We study the effects of gain and loss for coupled PT symmetric QC laser waveguides and show that TE0 and TE1 modes can be separated with proper choice of gain and loss values.