PT symmetry breaking in multilayers with resonant loss and gain locks light propagation direction

Novitsky, Denis V. and Karabchevsky, Alina and Lavrinenoko, Andrei V. and Shalin, Alexander S. and Novitsky, Andrey V. (2018) PT symmetry breaking in multilayers with resonant loss and gain locks light propagation direction. Physical Review B, 98 (12): 125102. ISSN 2469-9950

Abstract

Using the Maxwell-Bloch equations for resonantly absorbing and amplifying media, we study the temporal dynamics of light propagation through the -symmetric structures with alternating loss and gain layers. This approach allows us to precisely describe the response of the structure near the exceptional points of symmetry breaking phase transition and, in particular, take into account the nonlinear effect of loss and gain saturation in the symmetry broken state. We reveal that in this latter state the multilayer system possesses a lasinglike behavior, releasing the pumped energy in the form of powerful pulses. We predict locking of pulse direction due to the symmetry breaking, as well as saturation-induced irreversibility of phase transition and nonreciprocal transmission.