Thermal and band-filling effects in prism coupling to CdSSe-doped glass waveguides

G. Assanto

J. Mod. Opt. 36, 305-316 (1989)


Prism coupling is employed to investigate the nonlinear properties of CdS(0.9)Se(0.1) semiconductor-doped glass slab waveguides. Experiments performed with a nanosecond laser source show distributed-coupling phenomena typical of thermally-driven processes, with compensating effects due to band-filling contributions. Upon increasing the excitation level, a dramatic non-monotonic reduction in the coupling efficiency is observed, accompanied by asymmetries and multiple all-optical switching during the pulse evolution. Up to five distinct peaks can be recorded within a single Gaussian envelope, confirming the validity of travelling-wave-interaction model. This model is also used to interpret the oscillatory behaviour of output versus incident pulse energies in terms of simultaneously present Kerr and thermal nonlinearities. Finally, further evidence of the role of band-filling nonlinearities is obtained using a picosecond laser source.