Waveguide effect during photoetching of semiconductors

An optical waveguide formed near the surface of GaAs immersed in an etchant when it was illuminated with laser radiation. The time taken to form this waveguide was ~ 1 sec; in this time its thickness reached 47 μ and the change in the refractive index in the waveguide layer was Δ n≈0.1. This waveguide could have a decisive influence on the formation of diffraction gratings which appeared on illumination of the semiconductor in an etchant with one low-power laser beam.