Abstract

We demonstrate that surface plasma wave (SPW) effects result in the growth of high spatial frequency surface relief in thin photochemically deposited Cd films. Initially a weak SPW is excited by surface roughness-induced scattering from the incident field, the spatial modulation of the optical intensity resulting from the interference between the incident wave and the SPW promotes the growth of a periodic (ripple) structure which increases the scattering into the SPW. There is a positive gain coefficient increasing both the amplitude of the film structure and SPW intensity for spatial frequencies ranging from approximately the incident light wavevector to the SPW wavevector. The process, which is analogous to stimulated Raman scattering where the grating structure plays the role of the material excitation and the SPW corresponds to the Stokes beam, is the first demonstration of an exponentially growing instability involving surface electromagnetic waves.

© 1982 Optical Society of America