Waveguide-type acoustooptic frequency shifter driven by surface acoustic wave and its application to frequency-shifted feedback fibre laser

In this paper, a waveguide-type acoustooptic frequency shifter (AOFS) driven by a surface acoustic wave in a tapered crossed-channel proton-exchanged waveguide on a 128/spl deg/ rotated Y-cut LiNbO/sub 3/ substrate is demonstrated at an optical wavelength of 1.55 /spl mu/m. A 35% diffraction efficiency and 10% throughput are obtained at an input voltage of 10 V/sub rms/. Furthermore, frequency-shifted feedback laser oscillation with an AOFS module is realized, and an oscillation spectral width of 0.62 nm and a beat frequency spectral width of 12 kHz are demonstrated.