Intensity distribution of light emitted from a fiber tip mapped by short surface acoustic wave pulses

Laser generation of short surface acoustic wave (SAW) pulses with a fiber tip is demonstrated, In the experiments, a tapered optical fiber tip was used to guide the 532 nm radiation of a Nd:YAG laser with 180 ps pulse duration to the surface to be investigated. Due to the increasing spatial confinement of the laser radiation with decreasing tip-sample distance, SAW pulses with frequency components up to 1 GHz were excited in an aluminum film deposited on a quartz substrate. It is shown that thermoelastic excitation of elastic surface wave pulses provides a new tool for studying the spatial intensity distribution of the exciting laser light emanating from the aperture of a near-field optical device as a function of distance. (C) 1998 Elsevier Science B.V. All rights reserved.