Directly controlled deposition of antireflection coatings for semiconductor lasers

Reactive sputtering of silicon nitride was used to prepare single layer antireflection coating on one of the facets of a semiconductor laser. During the deposition the film thickness was controlled with two different methods. In the first case the laser was driven below its threshold current, and the light emitted from the facet being coated controlled the thickness. In the second case the lasing mode was used and the light from the rear facet of the laser was directed to the detector via an interference filter and used to monitor the decay of the lasing light. The residual reflectivity achieved was 10(-4).