Cavity Enhanced Techniques Using Continuous Wave Lasers

Helden, J. H. van; Peverall, R.; Ritchie, Grant A. D.

doi:10.1002/9781444308259.ch2

Cited by 15 publications

(19 citation statements)

References 31 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…If the mirror reflectivity, R is 99.24%, the cavity finesse is 411.8 from = √ /(1 − ); the width of the cavity resonance is 7.7 × 10 -6 cm -1 using = / [12,13], and the ratio of the maximum to the minimum intensity of the resonance profile is calculated to be 68700 [13]. The laser linewidth of a cw-QCL at a given frequency is approximately 5 × 10 -5 cm -1 [14]; the laser linewidth is still narrow in comparison to the FSReff by 2 orders of magnitude.…”

Section: Theory Of Off-axis Cavity Enhanced Absorption Spectroscopymentioning

confidence: 99%

Detection of shock-heated hydrogen peroxide (H2O2) by off-axis cavity-enhanced absorption spectroscopy (OA-CEAS)

Alquaity

Popov

et al. 2017

Appl. Phys. B

View full text Add to dashboard Cite

Cavity enhanced absorption spectroscopy (CEAS) is a promising technique for studying chemical reactions due to its desirable characteristics of high sensitivity and fast time response by virtue of the increased path length and relatively short photon residence time inside the cavity. Offaxis CEAS (OA-CEAS) is particularly suited for the shock tube applications as it is insensitive to slight misalignments, and cavity noise is suppressed due to non-overlapping multiple reflections of the probe beam inside the cavity. Here, OA-CEAS is demonstrated in the mid-IR region at 1310.068 cm-1 to monitor trace concentrations of hydrogen peroxide (H2O2). This particular probe frequency was chosen to minimize interference from other species prevalent in combustion systems and in the atmosphere. The noise-equivalent detection limit is found to be 3.25 x 10 −5 cm −1 , and the gain factor of the cavity is 131. This corresponds to a detection limit of 74 ppm of H2O2 at typical high-temperature combustion conditions (1200 K and 1 atm) and 12 ppm of H2O2 at ambient conditions (296 K and 1 atm). To our knowledge, this is the first successful application of the OA-CEAS technique to detect H2O2 which is vital species in combustion and atmospheric science.

show abstract

Section: Theory Of Off-axis Cavity Enhanced Absorption Spectroscopymentioning

confidence: 99%

Detection of shock-heated hydrogen peroxide (H2O2) by off-axis cavity-enhanced absorption spectroscopy (OA-CEAS)

Alquaity

Popov

et al. 2017

Appl. Phys. B

View full text Add to dashboard Cite

show abstract

“…However the resonators have strong constraints that make their implementation difficult. They require mirrors with reflectivities higher than 99.9% to achieve the needed finesse [5,6]. Although such mirrors are available with the right reflectivity, their bandwidth is still limited to a few nanometers in the mid-infrared.…”

Section: Introductionmentioning

confidence: 99%

Multicomponent gas analysis using broadband quantum cascade laser spectroscopy

Reyes-Reyes¹,

Hou²,

Mastrigt³

et al. 2014

Opt. Express

View full text Add to dashboard Cite

Abstract:We present a broadband quantum cascade laser-based spectroscopic system covering the region between 850 and 1250 cm −1 . Its robust multipass cavity ensures a constant interaction length over the entire spectral region. The device enables the detection and identification of numerous molecules present in a complex gas mixture without any pre-treatment in two minutes. We demonstrate that we can detect sub-ppmv concentration of acetone in presence of 2% of water at the same wavenumber region.

show abstract

“…These effects were quantified by the measured spectral SNR, defined as the ratio of the CEAS signal amplitude to the standard deviation (1σ ) of the noise present on the absorption-free portion of the spectrum. The signals output by the spectrometer were analysed by making use of the following equation [1][2][3] …”

Section: Experiments and Resultsmentioning

confidence: 99%

“…Among the most mature sensitivity-enhancing schemes are those making use of high-finesse optical cavities for extending the interaction length of the radiation through the gas sample, largely in the form of cavity ring-down spectroscopy (CRDS) and cavity enhanced absorption spectroscopy (CEAS) [1,2]. Despite the general consensus that higher levels of sensitivity can be achieved by the time-domain variant (CRDS), the extraction of absorption information from time-integrated intensity measurements (CEAS) is often preferred when designing field instrumentation, as it poses fewer engineering challenges.…”

Section: Introductionmentioning

confidence: 99%

RF noise induced laser perturbation for improving the performance of non-resonant cavity enhanced absorption spectroscopy

et al. 2014

View full text Add to dashboard Cite

We present a novel strategy for suppressing mode structure which often degrades off-axis cavity enhanced absorption spectra. This strategy relies on promoting small, random fluctuations in the optical frequency by perturbing the injection current of the diode laser source with radio frequency (RF) bandwidth-limited white noise. A fast and compact oxygen sensor, constructed from a 764 nm vertical-cavity surface-emitting laser (VCSEL) and an optical cavity with re-entrant configuration, is employed to demonstrate the potential of this scheme for improving the sensitivity and robustness of a field-deployable cavity spectrometer. The RF spectral density of the current noise injected into the VCSEL has been measured, and correlated to the effects on the optical spectral signal-to-noise ratio (SNR) and laser linewidth for a range of re-entrant geometries. A fourfold gain in the SNR has been achieved using the RF noise perturbation for the optimal off-axis alignment, which led to a minimum detectable absorption (MDA) predicted from an Allan variance study as low as 4.3 × 10(-5) at 1 s averaging. For the optically forbidden oxygen transition under investigation, a limit of detection (SNR = 1) of 810 ppm was achieved for a 10 ms acquisition time. This performance level paves the way for a fast, sensitive, in-line oxygen spectrometer that lends itself to a range of applications in respiratory medicine.

show abstract

Cavity Enhanced Techniques Using Continuous Wave Lasers

Cited by 15 publications

References 31 publications

Detection of shock-heated hydrogen peroxide (H2O2) by off-axis cavity-enhanced absorption spectroscopy (OA-CEAS)

Detection of shock-heated hydrogen peroxide (H2O2) by off-axis cavity-enhanced absorption spectroscopy (OA-CEAS)

Multicomponent gas analysis using broadband quantum cascade laser spectroscopy

RF noise induced laser perturbation for improving the performance of non-resonant cavity enhanced absorption spectroscopy

Contact Info

Product

Resources

About