Prism-type retroreflector of stable quarterwave retardance over extended spectral ranges

Abstract

The retardance introduced by a prism-type retroreflector depends on the refractive index of the prism material corresponding to the wavelength of the incident radiation and the values of the internal reflection angles. In normal-incidence devices (the external angle of incidence i=0°), the reflection angles θ are of fixed values and the retardance varies with the refractive index n. In this work, an oblique-incidence (i≠0), 3-reflection quarterwave retroreflector is presented which provides extreme stability of the retardance over extended spectral ranges. Between n=1.59 and n=1.73, the maximum deviation of the retardance from 90° is 0.1°. The device is suitable for use with laser beams.