Optical coatings for improved semiconductor diode laser performance

摘要

In this paper, we describe the development of electron cyclotron resonance plasma enhanced chemical vapour deposition (ECR-PECVD) process for the fabrication of silicon-oxynitride-based optical interference filters and passivation coatings on semiconductor laser facets. The use of in-situ ellipsometry as an effective tool for the monitoring and control of multilayer deposition processes is discussed, and it is shown that careful calibration of the ellipsometer is essential. Various corrections are applied, the most important of which takes into account the variation of the substrate temperature during the deposition of the thin film. Most of the SiN_x films were fabricated from tris(dimethylaminO)silane (TDAS, C_6H_(19)N_3Si) in an Ar plasma. Taking advantage of the inert character of these films, they were applied as encapsulants of sulfur treated Al_xGA_(1-x)As material. Silance (SiH_4) was used for the deposition of filmf of the type SiO_xN_y, and a-Si, providing a wider range of refractive indices than TDAS, thus allowing the implementation of more sophisticated interference filter designs.