Electrically Tunable Fabry-Perot Spectral Filter

Frequency-agile Fabry-Perot etalons have been built using the electro-optic actin of nematic and ferro-electric liquid crystals to tune the pass wavelength. Also, techniques exist for constructing liquid crystall elements in 1-D and 2-D arrays. The combination of these technologies would yield spatially addressable, tunable spectral filter elements useful for wavelength-domain optical signal processing. These devices would be compact, rugged, and require very low drive power. However, present commercial and research etalons exhibit unacceptably low finesse (F <= 20) and poor throughput in the visible range. In Phase I, we propose to build an etalon using liquid crystal material, and to assess those factors which limit the optical performance of practical 1-D and 2-D arrays in the visible and near-IR. Also, reliable spectral tuning and characterization of the array elements ot __/100 or better must also be demonstrated. Other concerns include the well-known thermal bowing of liquid crystal cells, and temperature effects of the liquid crystal tuning. These performance-limiting factors will be studied, and approaches developed for implementation in Phase II. We will also characterize the etalon's finess, transmission, extinction, useful spectral range, and response time, when filled with various liquid crystal materials to determine how liquid crystal paramaters (delta-n, ___, k33, Tc) affect overall performance, and to allow use of optimum materials.