4C-3 Monolithically Integrated Tandem Waveguide-Type Acoustooptic Frequency Shifter Driven by Surface Acoustic Waves

Abstract

A waveguide-type acoustooptic frequency shifter (AOFS) using coplanar AO coupling due to a surface acoustic wave (SAW), that is, Bragg diffraction, in a tapered crossedchannel proton-exchanged (PE) optical waveguide on a 128 • -rotated Y-cut LiNbO3 substrate for an optical wavelength of 1.55 µm has been proposed. In this study, a monolithically integrated tandem waveguide-type AOFS driven by SAW was designed and fabricated. The structure considered was a 2×4 optical switch, in which the input ports of two second 1×2 switches were connected to the two output ports of the first 2×2 switch on the same substrate. An interdigital transducer (IDT) with a period length of 32 µm and an overlap length of 2 mm was fabricated in the first and second stages of the AO interaction region. Diffraction efficiency was measured at a driving frequency of approximately 120 MHz. A diffraction efficiency of approximately 90% was obtained for each stage. When both stages were driven at the same frequency, a peak diffraction efficiency of 63% was obtained. Furthermore, the optical frequency shifts for the sum of two driving frequencies and the difference frequency ranging from DC to 5 MHz were observed.

Double-diffraction waveguide-type acousto-optic modulator with interchangeable input and output ports

“…Thus, these devices have been applied to a frequency shift feedback (FSF) fiber laser as an AO frequency shifter (AOFS). [1][2][3][4][5][6][7][8] On the other hand, recently, attention has been focused on the phase shift of a diffracted beam. Fang et al showed that a different phase shift between forward and reverse propagations can be obtained by inducing the photonic gauge potential due to photonic transitions.…”