High Brightness from an Unstable Resonator Mid-IR Semiconductor (Postprint)
AIR FORCE RESEARCH LAB KIRTLAND AFB NM
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We describe high-brightness, broad-area mid-IR semiconductor lasers. The optically pumped devices achieved higher brightness operation as unstable resonators. Each unstable resonator was realized by polishing or etching a diverging cylindrical mirror at one of the facets. For several mid-IR unstable resonator devices experimental near- and far-fields near threshold are shown, as well as at many times threshold. For an unstable resonator semiconductor laser operating at 4.6 micrometer and at a high peak power of 6.7 W the device was observed to be nearly diffraction limited 25 times threshold. In comparison a standard Fabry-Perot laser was observed to be 6 to 8 times diffraction limited when operated under similar conditions.
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