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We demonstrate the use of an Nd:YAG laser to optically pump an HBr gas laser, a concept combining the advanctages of solid-state and gas-laser technologies. A Q-switched Nd:YAG laser, tuned to 1.34 μm and frequency-stabilized, excites the v=3, J=5 state of HBr in a third-overtone transition. A diode laser locked to the HBr transition provides the seed signal for the Nd:YAG laser. Higher efficiencies than previously obtained for similar systems are expected in this concept because of the possibility of cascade lasing, which we have observed in our experiments and predicted in our simulations. Pump pulses of approximately 400-ns duration and 20-mJ energy are directed along the axis of a 1-m containing 15-torr HBr. In the currently unoptimized configuration, approximately 6 laser lines at about 4 μm are observed. The observed laser spectrum suggests collisional pumping for some lines and that intracavity atmospheric CO2 is a factor. We have developed and used a kinetic model, which shows good agreement with the experimental results. There is evidence of pure rotatioal lasing. Amplifiers are being added to increase the pump energy to 1 J.

Due to a narrow window of high atmospheric transmission near 4 microns, there is a great deal of interest for a scalable laser energy source in this spectral region. We propose a concept that combines the advantages of solid-state and gas laser technology. A Nd:YAG laser is tuned to 1.3391 microns by inserting an intracavity etalon and raising the operating temperature of the laser rod to 85 degree(s)C. This allows us to excite the v (0 →3), J (4 → 5) vibrational-rotational transition of HBr. To stabilize the frequency, a diode laser locked to this HBr transition seeds the Nd:YAG laser. Once excited, HBr can potentially lase in three subsequent steps to the ground state, emitting three photons in the 4-micron region. We present theoretical and experimental results demonstrating the operational principle of this laser system.