High-Power UV Lasers: Tunable Ultraviolet Burst-Mode Laser System Produces High-Energy Pulses
OHIO STATE UNIV COLUMBUS DEPT OF MECHANICAL ENGINEERING AND CHEMISTRY
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While planar laser-induced-fluorescence PLIF imaging of aerodynamic and combustion flows has developed enormously since its inception in the early 1980s, the ability to directly capture the dynamics of unsteady andor turbulent phenomena at high speed has been constrained by the difficulty of generating high-repetition-rate, broadly wavelength-tunable ultraviolet radiation with sufficient individual pulse energy. However, sources with all these characteristics have now been made possible by advances in the development of NdYAG-pumped optical-parametric-oscillator OPO systems operated in what has come to be known as pulse-burst mode. In combination with sum-frequency mixing, such systems have produced demonstrated output of around 0.5 or 1.0 mJ per pulse at 226 or 313 nm, respectively - sufficient to enable instantaneous nitric oxide NO and hydroxyl OH imaging at repetition rates as high as 250 kHz. While reported burst-mode NdYAG systems differ in detail, they share certain basic characteristics. Specifically, reported systems typically use a low-power on the order of 100 mW master oscillator typically NdYAG that is sliced into a burst train using either a pair of electro-optic Pockels cells or an acousto-optic deflector. In one exception, a repetitively Q-switched diode-pumped NdYVO4 laser is used as the master oscillator. The burst train is then amplified in a series of flashlamp-pumped NdYAG amplifiers. Typical reported burst sequences consist of between 8 and 40 pulses, with interpulse spacing as low as 1 microseconds, and individual pulse duration of between 6 and 25 ns.
- Lasers and Masers
- Test Facilities, Equipment and Methods