Semiconductor laser end-facet coatings for use in solid or liquid environments

An improvement for a semiconductor laser allows the facet reflectivity to be modified to compensate for the presence of a liquid or transparent solid medium having an index of refraction nm. A first dielectric coating is disposed on an end-facet of the semiconductor laser and has an index of refraction n1. A second dielectric coating is disposed on the first dielectric coating and has an index of refraction n2. The materials of the dielectric coatings are selected such that the fraction n1/n2= 2ROOT nm. Thus the problems associated with reductions of laser facet reflectivity due to being in contact with a surrounding medium which optically is very different from air is overcome.