Optical filter based on intracavity birefringent phase plates

We describe an optical filter, which consists of a pile of identical waveplates. Each plate is formed with an intracavity birefringent phase plate between two polarizers. We show that by means of such a configuration, which involves simultaneously two well-known effects in each plate: the interference of polarized light and the multiple-beam interference, the usual filter parameters, such as the peak bandwidth, the working range and the secondary maxima, can be managed by both the mirror reflectivity and the plate number (thus two degrees of freedom, instead of one). In consequence the implementation of narrow-band, large-working-range, small-crosstalk and low-loss optical filters becomes possible with a small number of weakly resonant phase plates. The principle of the filter is described and its transmission characteristics under some phase-matching condition are discussed.