Abstract

Infrared tunable picosecond pulses with a narrow spectral width are of considerable interest for the investigation of fast phenomena, e.g., in semiconductor materials with band gaps at infrared wavelengths. We describe the generation of such pulses by a short cavity dye laser (SCDL).¹ The SCDL system consists of a short Fabry-Perot cavity completely filled with dye and a three-stage amplifier. The cavity length is chosen such that only one or two axial modes are lasing within the emission range of the dye. Wavelength tuning is achieved by tuning the cavity length. An optoelectronic feedback loop provides wavelength stability. The cavity and amplifiers are pumped by the second harmonic of an actively/passively mode-locked Nd:YAG laser. The emission of the SCDL is measured temporally, spectrally, and spatially resolved for various cavity lengths, dye concentrations, and pump energies using the infrared dye LDS 820. Pumping with 35-ps (FWHM) pulses, the temporal width of the dye laser pulses ranges between 7- and 18-ps (FWHM) depending on the experimental conditions. The spectral width lies between 3 and 6 A and is determined by the relatively low cavity finesse used in the present experiments. An almost Gaussian spatial beam profile is achieved.

© 1985 Optical Society of America