Characterization of a 10.3-μm pulsed DFB quantum cascade laser

• Published in: Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy Vol. 63; no. 5; pp. 947 - 951
• Main Authors: Lytkine, A., Manne, J., Jäger, W., Tulip, J.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.04.2006
• Subjects: Absorption spectroscopy; Beam divergence; Frequency chirp; Frequency tuning; Quantum cascade laser; Absorption spectroscopy; Frequency tuning; Beam divergence; Frequency chirp; Quantum cascade laser
• ISSN: 1386-1425
• DOI: 10.1016/j.saa.2005.11.016

We have measured the output parameters of a 10.3-μm pulsed distributed-feedback (DFB) quantum cascade (QC) laser manufactured by Alpes Lasers and intended for high-sensitivity detection of ammonia and ethylene. The laser beam was collimated with an AR-coated aspheric ZnSe lens with focal length of 11.6 mm and clear aperture of 16.5 mm. Near- and far-field distributions of the laser emission were recorded with an infrared imaging camera. The fast-and slow-axis laser beam divergences were measured to be 1.2 and 1.4 mrad (FWHM), respectively. The divergence was found to be increasing with injection current. An air-spaced Fabry–Perot interferometer with free spectral range of 0.05 cm −1 was used to measure the frequency tuning rates of the laser. The laser was tuned by either heat sink temperature, injection current or pulse repetition rate with rates of ∼−8 × 10 −2 cm −1 K −1, −7 × 10 −2 cm −1 A −1 and −9 × 10 −4 cm −1 kHz −1, respectively. The laser frequency decreased linearly with a rate of 10 −2 cm −1 ns −1 (∼300 MHz ns −1) for laser pulses varied from 10 to 50 ns, and the frequency chirp rate was found to decrease for longer laser pulses.