Polarization switching of mutually coupled vertical-cavity surface-emitting lasers

Polarization switching (PS) of two mutually coupled vertical-cavity surface-emitting lasers (VCSELs) are studied numerically. A group of dimensionless rate equations is derived to describe our model. We focus on the influences of coupling rate and frequency detuning on PS dynamics. In the polarization-preserved mutual-injection case, x-polarization mode injection will defer the occurrence of PS, while y-polarization mode injection will lead PS to occur at a lower current. These influences will be weakened by frequency detuning. The effects of polarization-rotated injection are contrary to those of polarization-preserved injection. For polarization-rotated injection, two coupled VCSELs show really different PS characteristics if frequency detuning is nonzero. Besides in the L-I curves, we also find a region of values of the injection current where one laser emits in pure polarization mode, and the other laser emits in the orthogonal direction.