Generation of tunable subpicosecond pulses using low-Q dye cavities

The design and operation characteristics of a low-Q cavity dye laser chain pumped by a single laser (seeded Q-switched Nd:YAG) for generating high-power tunable subpicosecond pulses are presented. Two low-Q short dye cavities in cascade pumped well above threshold followed by extracavity pulse shaping in a highly saturated absorber and amplifiers lead to stable generation of single 500-fs pulses, i.e., a pulse-shortening factor > 10(4) (from a smooth 6-ns pump pulse). Output pulse energies of 500 microJ (1-GW peak power) are produced from 40-mJ pump energy and used to generate high-power tunable subpicosecond pulses from 450 to 700 nm by supercontinuum generation, spectral selection, and amplification in dye amplifiers pumped by the same Nd:YAG laser. The spectral and time processes involved in these pulse-shortening methods are discussed with a rate-equation model.