Abstract

Third-order optical interactions have a great potential for applications to all-optical signal processing and nonlinear surface spectroscopy.¹ Although the powers required for guided-wave nonlinear interactions are moderate, the strong beam confinement results in high enough power densities to cause changes in the refractive index of nonlinear waveguiding media. Therefore all guided-wave interactions that involve wavevector matching are affected, since the wavevector becomes power dependent. This includes distributed coupling into nonlinear waveguides by means of grating couplers, and in this paper we investigate this phenomenon. For example, we show that the coupling efficiency decreases with increasing power, making it difficult to achieve, within a waveguide, high power densities with standard gratings. However, we also show, both theoretically and experimentally, that chirped gratings lead to enhanced coupling efficiencies at high powers.

© 1989 Optical Society of America