An optical device comprising a glass prism that functions as a 180. degree. fold prism and a quarter-wave retarder. The optical device comprises a 180° folding glass prism having first and second total internal reflecting surfaces that provides a 90° phase shift of laser energy at a plurality of wavelengths propagating therethrough. The composition of the glass prism is selected so that its refractive index provides a 45° shift at each of first and second total internal reflecting surfaces. Dispersion in the glass is chosen to be small enough so that the phase shift of the energy propagating therethrough is relatively insensitive to wavelength. Consequently, the prism also functions as a quarter-wave retarder at the plurality of wavelengths.
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