Light-controlled perfect absorption of light.

We study coherent perfect absorption (CPA) of light in a Kerr nonlinear metal-dielectric composite medium, illuminated from the opposite ends. Elementary symmetry considerations reveal that equality of the incident light intensities is a prerequisite to ensure CPA in both linear and nonlinear systems for specific system parameters. We also derive the sufficient conditions for having CPA. We further show that, while CPA in a linear system is insensitive to the incident power level, in a nonlinear system CPA can be achieved only for discrete intensities with interesting hysteretic responses. Our unified formulation of CPA and waveguiding identifies them as opposite scattering phenomena. We further investigate light-induced CPA in on-resonant and off-resonant systems.