Reflection of a plane wave from a nonlinear absorbing medium

Notes on reflection and refraction of evanescent plane waves on the boundary between gainy/lossy media

“…8 Resolving the ambiguity in transition from lossy/gainy media to two lossless media Some time ago the above mentioned ambiguity has been widely discussed in literature, see eg [4][5][6][7], in connection with the so-called "enhanced total internal reflection" within the framework of so called active optical (dielectric) waveguides -dielectric waveguides having lossless core and gainy cladding (due to excitation by lasing effects from the pump signal) and operating in regime of total internal reflection. The modes in such active waveguides are amplified along the propagation path.…”

“…To remedy the situation some authors in [4][5][6][7] maintained that when the angle of incident wave reaches and exceeds the critical angle θ 1 = θ c then the direction of propagation of refracted wave n out ℓ2 should be taken in opposite x direction (ie towards the boundary), ie E A p (r) should propagate in n in ℓ2 direction instead of n out ℓ2 . In fact it means to take instead of E A p (r) = E out 2 (r) the wave E A p (r) = E in 2 (r) as given in (52).…”

Some remarks on enhanced total internal reflection

“…This leads to jump in the magnitude of the reflection factor from smaller to larger than one, ie to the amplification of the reflected wave with respect to the incident wave. In [3] the two-boundary-arrangement, ie a finite-thickness amplifying layer is analysed with subsequently limiting the thickness of the layer to infinity showing that then the enhanced TIR effects occur.…”

Observation of Poynting’s vector reversal in an active photonic cavity

“…It is therefore imperative to appreciate the subtleties involved in these non-Hermitian configurations where optical gain, which is usually far from resonance, interacts with confined fields in conjunction with coherent feedback provided by reflections at interfaces, coupling across barriers, or circulation in ring resonators. Indeed, the interplay between gain and feedback in a cavity can lead to a host of phenomena that are still not fully appreciated [29][30][31][32] and raises fundamental questions regarding causality [33][34][35][36]. A large number of theoretical studies have focused on this question, but experimental investigations are lacking.…”