Scaling of an Optically Pumped Mid-Infrared Rubidium Laser
AIR FORCE INSTITUTE OF TECHNOLOGY WRIGHT-PATTERSON AFB OH GRADUATE SCHOOL OF ENGINEERING AND MANAGEMENT
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An optically pumped mid-infrared rubidium Rb pulsed laser has been demonstrated in a heat pipe along the 62P32 - 62S12 transition at 2.730 micrometer and the 62P12 - 62S12 transition at 2.790 micrometer. The bleached limit, slope efficiency, and maximum laser output energy of the mid-IR Rb laser have been shown to scale linearly with increasing Rb density, contrary to prior laser demonstrations. A maximum output energy of 5 nJ per pulse had previously been observed before a rollover occurred in the scaling of output energy with Rb concentration. In this experiment, the maximum laser output energy observed was 100 nJ, with linear scaling to a Rb concentration of 7 x 10 to the 15th power cm-3. A maximum slope efficiency of 1.7 x 0.0001 was observed. Evidence that only a small percentage 2 of the available pump photons were absorbed at a concentration of 2 x 10 to the 15th power cm-3 and a pump energy of 10 muJ. This indicated that there were 20,000 pump photons per Rb atom at a pump energy of 10 mJ, and that the effective laser efficiency was 0.65 percent or higher. The hyperfine structure and absorption spectral profile of the 52S12 - 62P12 and 52S12 - 62P32 blue pump transitions were studied using a continuous wave cw pump source.
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