Logic gates and optical switching with vertical-cavity surface-emitting lasers

Abstract

We show that an index—and gain—guided vertical-cavity surface-emitting laser with a square-shaped active region can operate as a bistable laser with the two Gauss-Hermite modes ${\mathrm{TEM}}_{10}$ and ${\mathrm{TEM}}_{01}$. Optical switching from one mode to the other upon injection of appropriate Gaussian pulses is numerically investigated; the switching energy can be as small as 30 fJ and the process is completed in a time of the order of a few 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.