Acousto-optic devices of radiation frequency shift for optical-integrated sensors

Optical waveguides on ion-exchanged SiO2 (K+, Ag+) glass are perspective for monolithic optical-integrated schemes due to low optical losses, high temporal stability of their parameters, big sizes, low cost, high optical quality. The creation of efficient AO devices on non-piezoelectric substrate is rather difficult because of the necessity of film piezoelectric transducers fabrication, of secure SAW input in optical waveguide and of low AO quality coefficients of commercial glasses. Experimental investigation of the possibility of the creation of AO devices (frequency shifters, switches, modulators) on single mode and two-mode planar optical waveguides in ion-exchanged SiO2 glasses has been carried out in this work [1,2]. The central frequency of Bragg AO interaction was 200 MHz and frequency bandwidth was 1.5 MHz. SAW were formed by the following way. Aluminum interdigital electrodes were made by photolithography method on planar optical waveguides. ZnO texture piezoelectric film was deposited on the interdigital electrodes with primary orientation crystal axis C perpendicular to the film surface. The optimum film thickness was from 5.5 mu m to 6.5 mu m. The interdigital PZT had 100 pairs of electrodes with period 13.5 mu m and electrode width from 1.0 to 3.3 mu m for some different samples. The AO interaction length was 5 mm. Experimental results of diffraction efficiency for different samples were 4-8% at lambda = 0.63 mu m and about 3% at 1.06 mu m under electrical power 1 W on the PZT with matching network. These results show the possibility of film piezoelectric transducer utilizing for monolithic optical-integrated sensors.