Optimisation of laser linewidth and cavity alignment in off-axis cavity-enhanced absorption spectroscopy

Kasyutich, Vasili L.; Sigrist, Markus W.

doi:10.1016/j.infrared.2015.03.011

Cited by 7 publications

(2 citation statements)

References 44 publications

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“…[20] The residual mode noise suppression resulting from perturbation of the injection current is due to laser linewidth broadening, making it clear that tuned linewidth sources are advantageous in a laser spectrometer of this type. While this enhancement has been predicted theoretically [21], the actual impact of broadband RF perturbations on QCL linewidth requires further investigation.…”

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confidence: 88%

Broadening the optical bandwidth of quantum cascade lasers using RF noise current perturbations

2018

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We report on the broadening of the optical bandwidth of a distributed feedback quantum cascade laser (QCL) caused by the application of radio frequency (RF) noise to the injection current. The broadening is quantified both via Lamb-dip spectroscopy and the frequency noise power spectral density (PSD). The linewidth of the unperturbed QCL (emitting at ∼5.3 μm) determined by Lamb-dip spectroscopy is 680±170 kHz, and is in reasonable agreement with the linewidth of 460±40 kHz estimated by integrating the PSD measured under the same laser operating conditions. Measurements with both techniques reveal that by mixing the driving current with broadband RF noise the laser lineshape was reproducibly broadened up to ca 6 MHz with an increasing Gaussian contribution. The effects of linewidth broadening are then demonstrated in the two-color coherent transient spectra of nitric oxide.

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confidence: 88%

Broadening the optical bandwidth of quantum cascade lasers using RF noise current perturbations

2018

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“…Secondly, due to the residual discrete mode structure of the cavity transmission. The laser linewidth should be larger than the effective FSR of the cavity to efficiently suppress the spurious-coupling intensity noise [45]. In addition, any frequency jitter during the scanning across the molecular transition contributes towards the etalon effects in the residual signals.…”

Section: (A) the Main Shortcoming Of Oa-icos Is The Low Cavity Throughput (Transmitted Intensity Through The Cavity)mentioning

confidence: 99%

Experimental-based comparison between off-axis integrated cavity output spectroscopy and multipass-assisted wavelength modulation spectroscopy at 77 µm

et al. 2019

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A mid-infrared trace gas detection system based on off-axis integrated cavity output spectroscopy (OA-ICOS) is demonstrated for accurate and sensitive detection of N 2 O in combination with a continuous wave external-cavity quantum cascade laser (EC-QCL) working around 7.7 µm. A 13-times improvement in signal-to-noise ratio is achieved using a re-injection mirror and a minimum detection limit of 70 ppbv in less than 10 s averaging time is achieved, which yields a noise-equivalent absorption sensitivity (NEAS) of 6×10 −9 cm −1 Hz −1/2 . For comparison, a compact multipass cell is deployed to measure the same absorption line of N 2 O using wavelength modulation spectroscopy with second harmonic detection (WMS-2f). An enhancement factor of 20 in comparison to direct absorption spectroscopy (DAS) is achieved, yielding a minimum detection limit of 15 ppbv in less than 10 s averaging and a NEAS of 1×10 −9 cm −1 Hz −1/2 . A comprehensive comparison between the two systems is carried out in terms of residual amplitude noise (RAM), linearity, long-term stability, detection limit, spectral fitting, reproducibility, and background variations. The proposed sensor based on OA-ICOS is potentially advantageous for trace gas sensing in outdoor applications and harsh environments due to its robustness and flexibility of alignment.

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Cavity-enhanced absorption spectroscopy for shocktubes: Design and optimization

Chao

Shen

Sun

et al. 2019

Proceedings of the Combustion Institute

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Optimisation of laser linewidth and cavity alignment in off-axis cavity-enhanced absorption spectroscopy

Cited by 7 publications

References 44 publications

Broadening the optical bandwidth of quantum cascade lasers using RF noise current perturbations

Broadening the optical bandwidth of quantum cascade lasers using RF noise current perturbations

Experimental-based comparison between off-axis integrated cavity output spectroscopy and multipass-assisted wavelength modulation spectroscopy at 77 µm

Cavity-enhanced absorption spectroscopy for shocktubes: Design and optimization

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