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.