Collinear acoustical TM-TE mode conversion in proton exchanged Ti:LiNbO/sub 3/ waveguide structures

Collinear acoustooptic TM-TE mode conversion is experimentally investigated in proton exchanged Ti:LiNbO/sub 3/ optical waveguides. Their birefringence is adjusted by an appropriate annealing to allow phase matching at surface acoustic wave frequencies of about 90 MHz and 180 MHz, respectively. A planar mode converter with an efficiency of up to 90 percent is presented (87 MHz, 175 MHz). Furthermore, a combined acoustical/optical strip waveguide structure is developed as mode converter, leading to strongly reduced power requirements; only 0.3-mW acoustic power is sufficient to achieve a conversion efficiency of 50 percent.>