Grating-coupled external-cavity short-wavelength (λ ≈ 3.9 μm) InGaAs/InAlAs/AlAs quantum-cascade lasers

Bayrakli, Ismail; Wienold, Martin; Hempel, Martin; Klinkmueller, M.; Semtsiv, M. P.; Masselink, W. T.

doi:10.1007/s11082-010-9414-y

Cited by 5 publications

(1 citation statement)

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“…The tuning range is limited by the gain bandwidth of the gain medium. 31 The spectra are taken at the injection current of 300 mA at T ¼ 23°C. The maximum side mode suppression ratio is greater than 20 dB.…”

Section: External Cavity Lasermentioning

confidence: 99%

Ultrasensitive, real-time analysis of biomarkers in breath using tunable external cavity laser and off-axis cavity-enhanced absorption spectroscopy

Bayrakli

Akman

2015

J. Biomed. Opt

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A robust biomedical sensor for ultrasensitive detection of biomarkers in breath based on a tunable external cavity laser (ECL) and an off-axis cavity-enhanced absorption spectroscopy (OA-CEAS) using an amplitude stabilizer is developed. A single-mode, narrow-linewidth, tunable ECL is demonstrated. A broadly coarse wavelength tuning range of 720 cm⁻¹ for the spectral range between 6890 and 6170 cm⁻¹ is achieved by rotating the diffraction grating forming a Littrow-type external-cavity configuration. A mode-hop-free tuning range of 1.85 cm⁻¹ is obtained. The linewidths below 140 kHz are recorded. The ECL is combined with an OA-CEAS to perform laser chemical sensing. Our system is able to detect any molecule in breath at concentrations to the ppbv range that have absorption lines in the spectral range between 1450 and 1620 nm. Ammonia is selected as target molecule to evaluate the performance of the sensor. Using the absorption line of ammonia at 6528.76 cm⁻¹, a minimum detectable absorption coefficient of approximately 1×10⁻⁸ cm⁻¹ is demonstrated for 256 averages. This is achieved for a 1.4-km absorption path length and a 2-s data-acquisition time. These results yield a detection sensitivity of approximately 8.6×10⁻¹⁰ cm⁻¹ Hz(-1/2). Ammonia in exhaled breath is analyzed and found in a concentration of 870 ppb for our example.

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Section: External Cavity Lasermentioning

confidence: 99%