Abstract

We investigate the lensing and deflection of a weak picosecond pulse by symmetric and asymmetric refractive index profiles induced in doped and undoped Si and GaAs by a second pulse. Here, two 30-ps pulses at a wavelength of 1.064 μm are incident on the surface of the sample with a small angle between the two beams and an adjustable time delay between the two pulses. The absorption of the first pulse (by single- or two-photon absorption) creates a symmetric or an asymmetric index profile. The second pulse is simultaneously or subsequently defocused and/or deflected as it propagates through the sample by the spatial index profile created by the first pulse. We discuss several geometries in which we use these effects to construct multiple-beam optical limiters, and we carefully compare the performance of these devices with more conventional singlebeam devices operated in similar conditions. Finally, we illustrate the use of these phenomena in multiple-beam geometries as spectroscopic tools for measuring the sign and magnitude of nonlinear refractive index changes. Again, we compare these multiple-beam spectroscopic techniques with their single-beam counterparts.

© 1989 Optical Society of America