LOGIC GATES AND OPTICAL SWITCHING WITH VERTICAL-CAVITY SURFACE-EMITTING LASERS

We show that an index-and gain-guided vertical-cavity surface-emitting laser with a square-shaped active region can operate as a bistable la ser with the two Gauss-Hermite modes TEM lo and TEM,,. Optical switchi ng from one mode to the other upon injection of appropriate Gaussian p ulses is numerically investigated; the switching energy can be as smal l as 30 fJ and the process is completed in a time of the order of a fe w nanoseconds. We demonstrate the possibility of using the laser as a logic gate of the NOR, OR, NOT type. Carrier diffusion increases laser threshold and the size of the bistability domain, and it reduces both switching time and switching energy.