Kink-based mirrorless quasi-bistability in resonantly absorbing media

Optical bistability is the basic nonlinear phenomenon mediating the control of light by light, being of ultimate demand for a plethora of applications in laser information technologies. The two most general designs are driven by the presence or absence of an external feedback, among which the mirrorless architecture seems promising, being free of bulky mirrors, resonant cavities, photonic crystals, etc. In this Letter, we propose a method to achieve optical quasi-bistability governed by the formation of specific nonlinear waveforms called “kinks.” We show that a thin layer of the relatively dilute resonant medium specially designed to support kinks could serve as a platform for compact, ultrafast, low-power optical switching. This mechanism does not require high densities of resonant particles specific for the feedback-free devices driven by dipole–dipole interactions, and enhances the overall practical relevance of such devices for optical computing.