Nonlinear Coherent Perfect Absorption
  We review some of the recent concepts and their realization exploiting the perfect destructive interference of light in micro and nano structures. One refers to optical structures where the effective absorption can be controlled and maximized to perfect absorption. The reported effects depend crucially on the coherent nature of the exciting radiation. Achieved with a single (two or more) incident plane wave (waves) the effect carries the name of critical coupling (coherent perfect absorption). Thus in a system supporting critical coupling (CC) or coherent perfect absorption (CPA) all the incident radiation can be absorbed leading to null scattering. In particular all the incident light energy can be channeled into a specified mode of a multimodal structure if such modes are supported by the system. We present a brief overview of CC and CPA in linear systems to recount their underlying concepts as time-reversed lasing and some of their futuristic applications. Next we review our work on the nonlinear extensions of CC and CPA where one or more of the layered media could be nonlinear with Kerr-type nonlinearity. The dispersive nonlinearity is shown to offer a practical handle over the process of perfect absorption by incident laser power. Further we show that the nonlinear periodic structure can support gap solitons which absorbs all the incident energy and do not scatter any light outside the hetero-guide 
K. Nireekshan Reddy and S. Dutta Gupta
physics.optics