Real-time in situ monitoring of antireflection coatings for semiconductor laser amplifiers by ellipsometry

Very strict requirements need to be met for producing a high-quality single-layer antireflection coating on a traveling-wave laser amplifier facet. In order to obtain a facet reflectivity of 10/sup -4/ or less, the index of refraction and the layer thickness of single-layer coatings have to be controlled to better than 0.03 and 30 AA, respectively. An innovative approach to highly controlled antireflection layer deposition based on in situ real-time ellipsometry is presented. Index control within +or-0.01 and a facet reflectivity on the order of 10/sup -4/ are reproducibly obtained.>