Non-Hermitian skin effect in semiconductor photonic crystal slabs

The non-Hermitian skin effect is a recently discovered phenomenon in periodic wave systems, whereby a macroscopic number of eigenmodes become tightly localized near the boundaries in the presence of losses or amplification. Its demonstration with semiconductor photonic crystals could create new opportunities to engineer their spectral, angular, and spatial response for multiple device applications. However, previous theoretical work has only investigated this effect in purely one- or two-dimensional structures with ad-hoc (and unusually large) values of the imaginary refractive index. Here, we show numerically that strongly confined skin modes can be established in realistic Si photonic crystal slabs of finite thickness, even at photon energies below the Si absorption edge, where the only source of non-Hermiticity is radiation losses. Furthermore, these modes exhibit a distinctive chiral behavior that enables their selective excitation on opposite sample boundaries with free-space radiation incident along different directions.