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An analytical expression for the difference in buildup time between two longitudinal modes in a passively Q -switched laser resonator is developed and compared with experimental laser data. The results support the following temporal criterion for single-frequency, passively Q -switched operation: The difference in buildup time between any two longitudinal modes of the laser resonator should be comparable with or greater than the laser pulse duration to ensure single-frequency operation.

A systematic investigation of the tunability and efficiency of non-critically phase-matched (NCPM) and critically phase-matched (CPM) KTA OPOs using x-and ycut crystals orientations has been conducted for the first time. Using our previously developed tandem, KTA-CdSe, OPO technology, we demonstrate a multi-wavelength, mid-infrared source capable of simultaneously delivering tunable radiation in four broad bands covering the range from 1.5 to 10 µm with high conversion efficiency.

We report on several developments in solid state lasers and nonlinear optics specifically for applications in remote sensing. In the area of UV sources for ozone monitoring, we have developed an efficient, third-harmonic, tunable Ti:sapphire-laser-based source. For long-range, eyesafe detection of aerosols, we report a high-energy optical parametric oscillator (OPO) driven by a flashlamp-pumped, Q-switched Nd:YLF laser. Finally, for mid-infrared DIAL, we have developed a Tandem-OPO that converts a common Nd-doped laser into a tunable source capable of providing wavelengths in the range 1500-5500 nm and 8000-12000 nm. OZONE LIDAR SOURCEAtmospheric studies of ozone have been conducted successfully from both ground-based and aircraft-based systems employing a variety of sources that emit in the 285-to 315-nm region. The sources used to date for ozone DIAL work have included Nd:YAG-pumped, frequency-doubled dye lasers; Raman-shifted, quadrupled, Nd:YAG lasers; excimer lasers; and Raman-shifted excimer lasers. Existing aircraft and future space-based ozone measurements would benefit from coherent sources that are more efficient, compact, robust, reliable, and low-maintenance than those currently available.We describe here an all-solid-state laser transmitter, based on third-harmonic generation (THG) of a titanium-sapphire laser, that provides 35 mJ output pulses with 500-µs temporal separation in the 307-320 nm wavelength range. Ti:sapphire laserAs the tunable oscillator, we used an unstable-resonator, high-energy, gain-switched Ti:sapphire laser [1]. The laser was pumped by a high-energy, flashlamp-pumped, Q-switched, frequency-doubled, Nd:YLF laser configured for a 5-Hz, double-pulsed format. We achieved dual-wavelength operation of the Ti:sapphire laser by incorporating a mirror mounted on a high-speed galvanometer scanner that can rapidly switch the laser to any wavelength in the 920-960-nm range in a time less than the double-pulse separation of 500 µs.In order to reduce the Ti:sapphire laser linewidth and increase harmonic conversion efficiency [2] we injection-seeded the laser using two external-grating diode lasers (EOSI, Inc) tuned to regions around 925 nm and 945 nm, respectively. The linewidth of the Ti:sapphire laser was ~ 3-4 cm -1 in unseeded regime, and less than 0.007 cm -1 in seeded regime of operation.The main parameters of the pump Nd:YLF laser and unseeded Ti:sapphire tunable oscillator are given in Table 1. (When the Ti:sapphire laser was seeded the output energies were ~10-15% smaller).