Automatic power control of a VCSEL using an angled lid TO56 package

Many applications of semiconductor lasers require that the output power from the laser is maintained at a fixed level independent of temperature and aging, this is typically accomplished with edge emitting lasers using a back facet monitor photodiode which is incorporated into the laser package. The signal from the photodiode is used to drive the feedback control circuit. In the absence of a back facet it is necessary to develop an alternate packaging scheme for VCSELs that allows for the generation of a signal for use in maintaining a fixed output power. In this paper we present a VCSEL packaged in a TO56 can with a silicon pin photodetector. A portion of the emitted beam from the VCSEL is reflected from the lid onto the photodetector. Results demonstrating an auto-power control capability of ±3 percent are presented