Ultrafast All-Optical Switch with Switch-Off Time Unlimited by Carrier Lifetime

Abstract

All-optical switches are expected to become one of key elements in future ultrafast and flexible all-optical communication networks. And it has been generally believed that such all-optical devices would require very fast, as well as very efficient, nonlinear optical material (or phenomena). In fact, the well-known and often discussed figure of merit for nonlinear materials [n2/(ατ) , where n2 is the nonlinear refractive index change coefficient, α is the linear absorbance, and τ is the relaxation time] implies that it is the chosen nonlinear material that determines the basic device performance such as the switching speed and energy. In this paper, we show that this is not necessarily the case; the speed of a nonlinear optical switch proposed by the authors1,2 is not restricted by the slow relaxation time of high efficiency incoherent nonlinearities.