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4 May 1998 Tunable distributed-feedback quantum-cascade lasers for gas-sensing applications
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Continuously tunable single-mode emission of high performance quantum cascade (QC) lasers is achieved by application of the distributed feedback (DFB) principle. The devices are fabricated either as loss-coupled or index-coupled DFB lasers. Single-mode tuning ranges of approximately equals 100 nm have been measured in both of the atmospheric windows at emission wavelengths around (lambda) approximately equals 5 micrometer and 8 micrometer. Linear thermal tuning coefficients of 0.35 nm/K and 0.55 nm/K have been obtained above 200 K for (lambda) approximately equals 5 micrometer and 8 micrometer, respectively. The side-mode suppression ratio is better than 30 dB. Pulsed single-mode operation has been achieved up to room temperature with peak power levels of 60 mW. The lasers also operated single-mode in continuous wave at temperatures above liquid Nitrogen temperature; a single-mode tuning range of 70 nm has been measured in the temperature range from 20 K to 120 K. The gas sensing capabilities of the QC-laser have also been demonstrated using both direct absorption and wavelength modulation techniques. A pulsed, room temperature, QC-DFB laser operating at (lambda) approximately equals 7.8 micrometer was used to detect N2O diluted in N2. The detection limit was found to be approximately equals 500 ppb- m. In addition, the high resolution capability of the QC-DFB lasers (at 77 K) has been demonstrated via continuous, rapid- scan, direct absorption measurement of the Doppler limited R(16.5) lambda doublet of NO at (lambda) approximately equals 5.2 micrometer.
© (1998) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Claire F. Gmachl, Federico Capasso, Jerome Faist, Deborah L. Sivco, James N. Baillargeon, Albert L. Hutchinson, Alfred Y. Cho, Khosrow Namjou, Simin Cai, Edward A. Whittaker, James F. Kelly, Steven W. Sharpe, and John S. Hartman "Tunable distributed-feedback quantum-cascade lasers for gas-sensing applications", Proc. SPIE 3285, Fabrication, Testing, Reliability, and Applications of Semiconductor Lasers III, (4 May 1998);

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