Abstract

We present new experimental studies of the far-field scattering patterns produced by perturbed diffraction gratings consisting of equally spaced, gaussian-shaped grooves with randomly fluctuating depths. These surfaces, which have been fabricated in photoresist using a computer-controlled scanning apparatus, exhibit backscattering enhancement similar to that seen in light scattering from random surfaces with gaussian statistics. Through a series of measurements conducted on similar gratings with differing perturbation strengths, we probe the transition from the perturbed case (fluctuating groove depths) to the fully deterministic case (uniform groove depths). Since the polarization dependence of rough surfaces exhibiting backscattering enhancement is non-trivial and apparently related to multiple scattering, we also carefully investigate the polarization properties of these surfaces. Finally, we show how the power in various diffraction orders, for light scattered from a perfectly uniform grating of gaussian-shaped grooves, oscillates as the angle of incidence is changed — an interesting behavior that we believe is related to multiple scattering within the grooves.

© 1991 Optical Society of America