Reflective polarization retarder and laser apparatus utilizing same

Abstract

A reflective thin film polarization retardation device which is adapted for use in active mirror laser apparatus is described. The device permits obtaining phase retardation of light, different amounts of which may be readily obtained. Retardation results from interference effects within thin film arrays within the device. A polarization rotator utilizing the invention is made up of a thin film reflective transmissive polarizer, a thin film reflector and a phase adjusting layer, which may be one or more thin film layers. The phase adjusting layer is sandwiched between the thin film polarizer and the thin film reflector. The thin films constituting the polarizer, phase adjusting layer and reflector may be successively deposited on one of the planar faces of a body of laser glass, with the films constituting the polarizer being deposited first. The s polarization component of the incident light, which may be linearly ploarized laser light, is reflected by the polarizer and the p component of the incident light is transmitted through the polarizer and the phase adjusting layers to the reflector. The retardation interposed by the assembly is tuned by the phase adjusting layer which provides the desired amount of phase shift between the reflected s and p components. The phase shift may be (temporally) 180.degree. such that incident, linearly polarized light in the laser glass is converted to the orthogonal polarization, thus avoiding interference effects in the laser glass.

Dependencies are inferred from the claim text.