Distributed couplers, such as prisms and gratings, have been largely employed in conjunction with nonlinear planar waveguides in order to study the nonlinear properties of the structures, suitable for all optical devices in integrated optics. In the present work we report an experimental investigation of a semiconductor nonlinear grating coupler realized onto a planar linear waveguide, where the grating is burried between the guide and the substrate the periodicity is 0.8 microns but over the guide in correspondence of the grating, there is a thin layer 200 A of CdS. A single mode Lambda 0.632 microns is supported by the guide while two modes are present if an Ar laser or the second harmonic of Nd-Yag pulsed laser is used. Radiation is coupled out through a prism . Input coupling effects have been studied in both temporal c.w. and pulsed regime versus input power. In c.w. operation all the obtained results are interpreted in terms of optothermal dispersive and absorbitive effects, while in the ps time domain electronic nonlinear behaviour of the CdS is the main responsible of the refractive index change of CdS.
This article is from 'OSA Proceedings of the Topical Meeting on Nonlinear Guided-Wave Phenomena Held in 2-4 September 1991. Cambridge, England United Kingdom. Volume 15', AD-A253 471, p312.