Sensitivity enhancement of off-axis ICOS using wavelength modulation

Malara, P.; Witinski, Mark F.; Capasso, Federico; Anderson, James G.; Natale, P. De

doi:10.1007/s00340-012-4975-z

Cited by 23 publications

(11 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Here, α CEAS is the measured, cavity-enhanced absorption and G is the cavity gain set by the mirror reflectivity (determined by CRDS or calibration). CEAS has been used extensively in high-finesses configurations for trace-gas sensing [145,146,147,148] and the use of WMS has also been explored [149], however, like CRDS these methods suffer from long cavity residence times and susceptibility to mirror fouling. Recently, low finesse (gain of 100× in path length) cavities have been integrated into shock tubes to improve the measurement sensitivity of combustion species while maintaining measurement rates (≈100 kHz) sufficient to resolve reaction kinetics [150,151] and these studies are highlighted in Section 7.1.…”

Section: Cavity-enhanced Techniquesmentioning

confidence: 99%

Infrared laser-absorption sensing for combustion gases

Goldenstein

Spearrin

Jeffries

et al. 2017

Progress in Energy and Combustion Science

526

197

View full text Add to dashboard Cite

Infrared laser-absorption spectroscopy (IR-LAS) sensors play an important role in diagnosing and characterizing a wide range of combustion systems. Of all the laser-diagnostic techniques, LAS is arguably the most versatile and quantitative, as it has been used extensively to provide quantitative, species-specific measurements of gas temperature, pressure, composition and velocity in both laboratory-and industrial-scale systems. Historically, most IR-LAS work has been conducted using tunable diode lasers, however, today's researchers have access to a wide range of light sources that provide unique sensing capabilities and convenient access to nearly the entire IR spectrum (≈1 to 20 μm). In particular, the advent of room-temperature wavelength-tunable mid-infrared semiconductor lasers (e.g., interband-and quantum-cascade lasers) and hyperspectral light sources (e.g., Fourierdomain mode-locked lasers, dispersed supercontinuum lasers, and frequency combs) has provided a number of unique capabilities that combustion researchers have exploited. The primary goal of this review paper is to document the recent development, application, and current capabilities of IR-LAS sensors for laboratory-and industrial-scale combustors and propulsion systems. A thorough review and description of the fundamental spectroscopy governing the accuracy of such sensors, and recent findings and databases that enable improved modeling of molecular absorption spectra will be provided. Modern light sources and the most commonly used diagnostic techniques are also discussed.

show abstract

Section: Cavity-enhanced Techniquesmentioning

confidence: 99%

Infrared laser-absorption sensing for combustion gases

Goldenstein

Spearrin

Jeffries

et al. 2017

Progress in Energy and Combustion Science

526

197

View full text Add to dashboard Cite

show abstract

“…For laser powers of 20 mW to 100 mW, representing typical values for quantum cascade lasers (QCL) commonly employed in the mid-infrared (IR) range, this corresponds to noise equivalent absorption coefficients (NEA) of 10 −8 cm −1 Hz −1/2 and above. On the contrary, direct absorption spectroscopic sensing is now commonly performed in the mid-IR range well below 10 −9 cm −1 Hz −1/2 using multipass absorption cells [5,6] or even below 10 −10 cm −1 Hz −1/2 using different techniques of cavity-enhanced spectroscopy [7][8][9]. Continued efforts are taken to exploit the advantages of PAS while, at the same time, achieving or exceeding the sensitivity of TLAS, e.g.…”

Section: Introductionmentioning

confidence: 99%

Mid-infrared sensing of CO at saturated absorption conditions using intracavity quartz-enhanced photoacoustic spectroscopy

et al. 2019

View full text Add to dashboard Cite

The sensitivity of quartz-enhanced photoacoustic spectroscopy (QEPAS) can be drastically increased using the power enhancement in high-finesse cavities. Here, low noise resonant power enhancement to 6.3 W was achieved in a linear Brewster window cavity by exploiting optical feedback locking of a quantum cascade laser. The high intracavity intensity of up to 73 W mm −2 in between the prongs of a custom tuning fork resulted in strong optical saturation of CO at 4.59 µm. Saturated absorption is discussed theoretically and experimentally for photoacoustic measurements in general and intracavity QEPAS (I-QEPAS) in particular. The saturation intensity of CO's R9 transition was retrieved from power-dependent I-QEPAS signals. This allowed for sensing CO independently from varying degrees of saturation caused by absorption induced changes of intracavity power. Figures of merit of the I-QEPAS setup for sensing of CO and H 2 O are compared to standard wavelength modulation QEPAS without cavity enhancement. For H 2 O, the sensitivity was increased by a factor of 230, practically identical to the power enhancement, while the sensitivity gain for CO detection was limited to 57 by optical saturation.

show abstract

“…In correspondence of the π-FBG reflectivity drop, the two wings of these split-resonances are partially overlapped, and their interference leads to an extremely narrow notch figure in the transmission spectrum. The described interference pattern can be much sharper than the resonance of the isolated π-FBG, and is easily detectable with a robust technique known in spectroscopy as integrated cavity output [10]. As a consequence, the Bragg wavelength of a π-FBG can be tracked with a significantly improved resolution in the closed-loop configuration, at no Fig.…”

mentioning

confidence: 97%

“…To record the smooth envelope of the π-FBGRR interference patterns an integrated cavity output technique is used [10]. The wavelength of a DFB laser diode with a 20-MHz linewidth is scanned at a 100-Hz frequency across the central resonance of the π-FBG.…”

mentioning

confidence: 99%

Enhanced spectral response of π-phase shifted fiber Bragg gratings in closed-loop configuration

et al. 2015

Self Cite

View full text Add to dashboard Cite

The transmission spectrum of a ring resonator enclosing a π-phase shifted fiber Bragg grating (π-FBG) shows a spectral feature at the Bragg wavelength that is much sharper than resonance of the π-FBG alone, and that can be detected with a simple integrated cavity output technique. Hence, the resolution of any sensor based on the fitting of the π-FBG spectral profile can be largely improved by the proposed configuration at no additional fabrication costs and without altering the sensor robustness. A theoretical model shows that the resolution enhancement attainable in the proposed closed-loop geometry depends on the quality factor of the ring resonator. With a commercial grating in a medium-finesse ring, a spectral feature 12 times sharper than the π-FBG resonance is experimentally demonstrated. A larger enhancement is expected in a low-loss, polarization maintaining setup.

show abstract

Sensitivity enhancement of off-axis ICOS using wavelength modulation

Cited by 23 publications

References 17 publications

Infrared laser-absorption sensing for combustion gases

Infrared laser-absorption sensing for combustion gases

Mid-infrared sensing of CO at saturated absorption conditions using intracavity quartz-enhanced photoacoustic spectroscopy

Enhanced spectral response of π-phase shifted fiber Bragg gratings in closed-loop configuration

Contact Info

Product

Resources

About