Thin film semiconductor waveguide with large optical nonlinearities for generating sound and third harmonic waves

Nonlinear optical interactions in the thin film waveguide have advantages for the high energy density inside the film as well as the phase matching capability between propagating modes. By use of vacuum-deposited ZnS thin film on the BK-7 glass substrate, experiments were performed on the harmonic generation of Nd:YAG laser to examine the nonlinearity of polycrystalline films. A Q-switched Nd:YAG laser beam at three wavelengths around 1.064µm with peak power of 3-5kW was focussed onto the prism coupler to excite the TE mode inside the film. The second harmonic wave as well as third harmonic wave were observed by this experiment, and this result demonstrates the large second Order nonlinearities in the orientated polycrystalline thin film waveguide.