Polarizer-free acousto-optic monochromators

Monochromators based on a noncollinear acousto-optic filter without external polarizers have been studied. As an element to select an operating diffracted light beam, (1) a spatial filter-telescope and (2) an output plane of a filter crystal rotated in a diffraction plane have been used. In the latter case, dispersion of the acousto-optic filter crystal is compensated using a correcting prism made from the same crystal and placed behind an output filter plane along a path of a filtered light beam. As a result, the transmission coefficient of the monochromator is increased upon an effective compensation of the angular drift of the filtered light beam, the monochromator design is simplified, and its sizes are decreased.