POLARIZATION-INDEPENDENT ACOUSTICALLY TUNABLE OPTICAL FILTER

A polarization-independent acoustically tunable optical filter is described, with 1.3 nm bandwidth and 145 nm tuning range demonstrated about a center wavelength of 1525 nm. Filtered and unfiltered beams exit from different ports of this 2×2 integrated-optic structure fabricated on a LiNbO 3 substrate. The filter conversion efficiency was 97% for unpolarized light, limited by imperfect splitting of the directional-coupler polarizing beamsplitters. Using an unpolarized, 105-nm-wide light-emitting diode as the optical source, 16 dB isolation of the filtered port was achieved, both with respect to the nearest nulls and the remote background spectrum.