Ferroelectric liquid-crystal tunable filter

A new discrete-channel tunable Lyot filter that uses ferroelectric liquid-crystal (FLC) smectic C* wave plates is described and demonstrated. The device is tuned by changing the retardation of each birefringent element. This is achieved by electrically rotating the FLC wave plates in each stage by 45 degrees , which effectively changes the design wavelength of the Lyot filter. The transmission characteristics of such a device are demonstrated in a three-stage filter and show good agreement with theory. Advantages of the FLC tunable filter over existing filter structures include low switching voltages (+/-10 V), rapid tunability (~100 kHz), potentially high transmission and wide field of view, and large entrance aperture.