Gigawatt Picosecond Dye Lasers and Ultrafast Processes in Semiconductor Lasers

Citation

Koch, Thomas Lawson (1982) Gigawatt Picosecond Dye Lasers and Ultrafast Processes in Semiconductor Lasers. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/61ca-rp72. https://resolver.caltech.edu/CaltechETD:etd-10042006-130634

Abstract

This thesis is a theoretical and experimental investigation of a gigawatt picosecond dye laser oscillator-amplifier system, and the application of that system to the study of ultrafast lasing and carrier dynamics in semiconductor lasers.

Beginning with a review of traveling wave rate equations, nonlinear pulse propagation in a generalized two-level amplifying/absorbing medium is discussed. This permits a qualitative treatment of synchronously mode-locked dye lasers. The formalism is then refined to provide a quantitative analysis of picosecond dye laser amplifier chains, including amplified spontaneous emission, saturable absorbers used for amplifier stage isolation, gain saturation with "angular hole-burning" and triplet losses, and linear and nonlinear pulse shaping effects.

Experimentally, the construction and operation of a three stage Nd:YAG laser pumped picosecond dye laser amplifier chain is described. Numerical modeling is used to compare the theoretical analysis with the experimental results. In addition, a brief discussion of picosecond time domain measurement techniques is presented, focussing on nonlinear optical methods. This includes a parametric sum frequency upconversion gating technique used extensively in this work to provide linear, picosecond resolution temporal measurements of optical pulses which are synchronized to the dye laser pulses.

The output of the picosecond dye laser system is used to optically generate high carrier densities in semiconductor lasers, and the ensuing short pulse lasing dynamics are investigated and compared to the predictions of a simple rate equation analysis. Novel effects are observed in the spectrally resolved temporal measurements of the lasing output from picosecond optically pumped buried heterostructure semiconductor lasers. A model is developed which includes both broadband stimulated emission as well as many-valley and hot electron effects in the semiconductor, and the model is in close agreement with the observed behavior. The conclusion is drawn that the picosecond lasing dynamics of semiconductor lasers can be understood if the conventional rate equations are abandoned in favor of a more fundamental analysis which includes not just the dynamics of the optical energy exchange in the laser cavity, but the detailed picosecond dynamics of the semiconductor material as well.

Thesis Files