Abstract: A beam of light issued by a light source enters a catadioptric arrangement and initially travels therethrough along an axis. At least one lens is situated at the axis and is axially delimited by two curved major surfaces having respective centers of curvature. The beam of light is reflectively diverted from the axis and travels in a path which includes a path section that is directed at one of the major surfaces and has such a spatial orientation relative to the axis and the major surfaces that light traveling in this path section bypasses the centers of curvature and impinges all regions of the major surfaces at angle deviating from respective normals to the regions with attendant avoidance of specular retroreflection from such regions.

Abstract: A laser employs a Fabry-Perot etalon, coupled to an optical cavity, to control either the power or the frequency of the laser substantially independently.