POLARIZATION-INDEPENDENT INTEGRATED OPTICAL, ACOUSTICAL TUNABLE DOUBLE-STAGE WAVELENGTH FILTER IN LINBO3

We report a polarization-independent integrated acousto-optical double -stage wavelength filter in X-cut, Y-propagating LiNbO3. The device co nsists of a combination of four acousto-optical mode converters, a TE- and a TM-pass polarizer, and two polarization splitters; their specif ic design and properties are discussed. The filter has a bandwidth of 1.4 nm and a tuning range of 76 nm around lambda almost-equal-to 1.55 mum. Maximum filter transmission is achieved with a RF drive power of only 80 mW; it excites via a single unidirectional transducer a guided surface acoustic wave driving the four polarization converters of bot h stages. Fiber-to-fiber insertion loss is 4.6 dB for TM- and 4.8 dB f or TE-polarized waves. Multiwavelength filtering has been demonstrated .