Spectral singularities and tunable slab lasers with 2D material coating

Abstract

We investigate linear and nonlinear spectral singularities in the transverse electric and transverse magneticmodes of a slab laser consisting of an active planar slab sandwiched between a pair of Grapheneor Weyl semimetal thin sheets. The requirement of the presence of linear spectral singularities gives thelaser threshold condition while the existence of nonlinear spectral singularities due to an induced weakKerr nonlinearity allows for computing the laser output intensity in the vicinity of the threshold. Thepresence of the Graphene and Weyl semimetal sheets introduces additional physical parameters that wecan use to tune the output intensity of the laser. We provide a comprehensive study of this phenomenonand report peculiarities of lasing in the TM modes of the slab with Weyl semimetal coatings. In particular,we reveal the existence of a critical angle such that no lasing seems possible for TM modes of the slab withsmaller emission angle. Our results suggest that for TM modes with emission angle slightly exceedingthe critical angle, the laser output intensity becomes highly sensitive to the physical parameters of thecoating.