Grant Lythe's publications: up to Dec. 1997

1. Semiconductor laser dynamics

with T. Erneux

Optique nonlinéaire théorique, Université Libre de Bruxelles CP231, Bruxelles 1050 BELGIUM

and A. Gavrielides and V. Kovanis

Nonlinear Optics Center, Phillips Laboratory PL/LIDN, Kirtland AFB, NM 87117-5776

Semiconductor lasers have a wide range of applications because they are of relatively small size, they can be massively produced at low cost, and they are easy to operate. Despite their successful technology, semiconductor lasers are very sensitive to any external perturbation. A small amount of optical feedback resulting from the reflection from an optical disk or from the end of an optical fiber is sufficient to generate pulsating instabilities. Systematic experimental studies of semiconductor lasers, in particular time series analysis, is not possible because the timescale of the intensity pulsations is typically in the picosecond regime. Fourier spectra measurements show a gradual increase of oscillatory instabilities as parameters are changed but do not reveal what are the bifurcation mechanisms. Most of the progress on our understanding of these bifurcations comes from extensive numerical studies of simple models and their comparison to the experimentally obtained Fourier spectra.

2. Stochastic calculus and noise-controlled dynamics

Small amounts of noise can dramatically change and simplify non-equilibrium dynamics. Examples include slow-fast dynamics, when long quiescent phases are occassionally interrupted by bursts of activity; and spatially extended systems undergoing pattern-forming transitions such as annealing and the formation of convective patterns. Macroscopic length- and time-scales are found to emerge from microscopic fluctuations.

3. Very-high-energy gamma-ray astronomy

with the JANZOS collaboration

Cosmic rays withe extremely high energies bombard the earth's atmosphere. Where do they come from? One possibility is supernovae. The JANZOS experiment was built to scan the southern sky for sources of very-high energy (TeV) and ultra-high-energy (PeV) gamma rays. In particular, the supernova SN1987A was shown not to be a significant source.