High-efficiency acoustooptic guided-mode to leaky-mode conversion in proton-exchanged lithium niobate waveguides

The detailed results of an experimental study on high-efficiency collinear acoustooptic interaction in proton-exchanged lithium niobate (PE:LiNbO
₃
) are presented. The guided-to-leaky mode-conversion for an optical beam at the wavelength of 0.6328 μm has been measured for different surface acoustic wave (SAW) carrier frequencies on x- and z-cut PE:LiNbO
₃
. An optical guided TM mode to substrate TE mode conversion with efficiency as high as 77% has been observed with a SAW center frequency of 367 MHz and an input RF drive power density of 65 mW/mm on z-cut LiNbO
₃
. In addition, an optical guided TE mode to substrate TE mode conversion with efficiency of 90% has been observed with a SAW center frequency of 103 MHz and an input RF drive power density of 94 mW/mm on x-cut LiNbO
₃
.