A diode-pumped Cr:LiSAF laser for UAV-based water vapor differential absorption lidar (DIAL)

• Main Authors: Prasad, C.R., Fromzel, V.A., Smucz, J.S., Hwang, I.H., Hasselbrack, W.E.
• Format: Conference Proceeding
• Language: English
• Subjects: Diodes; Electromagnetic wave absorption; Laser excitation; Laser radar; Laser tuning; Pump lasers; Space vector pulse width modulation; Tunable circuits and devices; Unmanned aerial vehicles; Wavelength measurement
• DOI: 10.1109/IGARSS.2000.857241

An autonomous, compact, high-energy, injection seeded, diode-pumped, tunable Cr:LiSAF laser for a water vapor differential absorption lidar (DIAL) system deployed on a high-altitude unpiloted airborne vehicle (UAV) has been developed. A unique laser resonator, consisting of a Cr:LiSAF slab pumped by 8 high-power diode bar stacks in a total internal reflection configuration, provides high extraction efficiency and good laser beam quality. Output pulse energies of >35 mJ at 834 nm and 25 mJ at 816 nm, with pulse widths of /spl sim/90 ns at 6 Hz pulse repetition rate, were obtained. A linewidth of less than 0.01 cm/sup -1/ was achieved by injection seeding with an 816 nm DFB diode laser. Using a photo-acoustic cell (PAC), an innovative seeding system was utilized to lock the DFB laser wavelength to a water vapor absorption line and to consistently seed the slave laser at a desired wavelength within the absorption line. A high spectral purity (>99%) and excellent tuning performance were demonstrated. Water vapor profiles measured with a DIAL system utilizing this laser compare well with radiosonde data taken before and after the measurements.