Enhancing Optical Bistability in Photonic Crystals

All-optical devices have attracted much attention in the last years as a response to the increasing request for high speed communication and data processing. So much effort has been devoted to realize optical switches, logic gates and memory with structures such as micro-ring resonators [1] and photonic crystals [2]. Photonic crystals have received special attention recently in which optical bistability [3] is the major phenomenon to be realized.Nonlinearity is an inevitable requisite for optical bistability. To obtain a low power, fast bistable behavior, enhanced nonlinearity is essential besides the proper feedback mechanism. In experiment, one might use two-photon absorption, thermo-optic effect, Kerr effect, etc. to provide the nonlinearity. A reluctant trade-off is that if the nonlinear effect is strong, its time response becomes slow, e.g. the resulting optical bistability from the Kerr effect, which is the fastest process with time response of about 1-10fs [4], can be almost ignored if the pulse duration is more than a few hundreds of nanoseconds [5]. For higher speed, we should optimize the structure or utilize materials with stronger nonlinearity to enhance optical bistability. In this work, we try to enhance nonlinearity with a change in a structure similar to the one mentioned in [2] and using more nonlinear materials