Abstract

Plasmon surface polaritons (PSPs) exist as collective oscillations of the electron density at a metal surface. These longitudinal polarization waves are confined to the metal surface, since they decay exponentially in the direction normal to the surface. Optical coupling to the PSP occurs when there is a periodic or random surface structure which allows the parallel component of the incident wave vector to match the PSP wave vector. Enhanced optical absorption will occur depending on the incident optical frequency and polarization, surface roughness parameters and orientation, angle of incidence, and the metal’s dielectric properties. Photothermal techniques offer an ideal way to study such nonradiative processes since only the absorbed portion of the incident energy contributes to the photothermal signal. In particular, the pyroelectric thin-film calorimeter is well suited for this purpose due to its extreme sensitivity of a few nanojoules and a time resolution of better than 100 ns. Periodic and randomly rough metal surfaces were investigated using both cw and pulsed lasers. Results are presented for a variety of surface roughness conditions.

© 1988 Optical Society of America