The present invention concerns an anti-reflection coating for
semiconductor lasers, in particular a coating on the laser facet with
advantageous properties resulting in improved reliability and reduced
probability of specific breakdowns, especially so-called catastrophic
optical damages (CODs). It is a quarter-wave coating with a predetermined
reflectivity, preferably between 0 and 10% and consists of or comprises
SiN.sub.x:H. It is preferably applied by a Plasma-Enhanced Chemical Vapor
Deposition (PE-CVD) process whose process parameters are controlled such
that a desired optical thickness and refractive index of the coating are
achieved. The PE-CVD process may be controlled to result in an Si/N ratio
between about 0.5 and 1.5 and/or to produce a coating of essentially
amorphous SiN.sub.x:H whose density approaches the density of crystalline
Si.sub.3N.sub.4.