Mode control of vertical-cavity surface-emitting lasers by germanium coating

Abstract

We have successfully developed a selective surface coating technique to control the modal behavior of the ion-implanted vertical-cavity surface-emitting laser (VCSEL). With selective deposition of a germanium coating by the lift-off process, we could spatially control the threshold gain condition of the VCSEL to support the single transverse mode. The threshold current is 7 mA and single transverse mode operation is maintained up to I mW. The method is simple and nondestructive compared with other techniques.