Integrated acousto-optic frequency shifter with surface acoustic wave

Integrated optical rotation sensor (IORS) is a new type of optical sensors. In this paper, an integrated acousto-optic frequency shifter (AOFS) with surface acoustic wave (SAW) is developed as one of key integrated elements of IORS. The design, fabrication and test of acousto-optic frequency shifter with SAW are presented. The wedge of zinc oxide film on glass substrate is designed as new structure for using in IORS. Experimental results show that the performance of zinc oxide film is stable, the linearity of zinc oxide wedge is suitable for improving Bragg diffraction efficiency, and some good mono-mode performances of planar waveguide are obtained. The frequency shift of 198 MHz plus or minus 0.75 MHz, diffraction efficiency of 8% (at optical wavelength of 0.63 micrometer), and 3 - 5% (at optical wavelength of 1.06 micrometer) are obtained at 1 Watt of electrical power. These experimental results satisfy the main requirements of IORS. High frequency stability is the main specification of RF driving circuits for using SAW AOFS in IORS. In this paper, a new digital scheme based on direct digital synthesis is presented for improving frequency stability.