13 research outputs found
Small-Size Resonant Photoacoustic Cell of Inclined Geometry for Gas Detection
A photoacoustic cell intended for laser detection of trace gases is
represented. The cell is adapted so as to enhance the gas-detection performance
and, simultaneously, to reduce the cell size. The cell design provides an
efficient cancellation of the window background (a parasite response due to
absorption of laser beam in the cell windows) and acoustic isolation from the
environment for an acoustic resonance of the cell. The useful photoacoustic
response from a detected gas, window background and noise are analyzed in
demonstration experiments as functions of the modulation frequency for a
prototype cell with the internal volume ~ 0.5 cm^3. The minimal detectable
absorption for the prototype is estimated to be ~ 1.2 10^{-8} cm^{-1} W
Hz^{-1/2}.Comment: 11 pages, 5 figure
Photoacoustic spectroscopy using quantum-cascade lasers
Contains fulltext :
100921.pdf (publisher's version ) (Open Access
Detection of trace gases by rapidly-swept continuous-wave cavity ringdown spectroscopy: pushing the limits of sensitivity
Fast, low-noise, mode-by-mode, cavity-enhanced absorption spectroscopy by diode-laser self-locking
Ultraviolet Laser Plasma Preionization and Novel Thomson Scattering Method for Weakly Ionized Discharges
A quantum cascade laser-based optical feedback cavity-enhanced absorption spectrometer for the simultaneous measurement of CH4 and N2O in air
Multi-mode absorption spectroscopy, MUMAS, using wavelength modulation and cavity enhancement techniques
Spectral line-shapes investigation with Pound-Drever-Hall-locked frequency-stabilized cavity ring-down spectroscopy
A review of recent experiments involving a newly developed Pound-Drever-Hall-locked frequency-stabilized cavity ring-down spectroscopy (PDH-locked FS-CRDS) system is presented. By comparison to standard FS-CRDS, the PDH lock of the probe laser to the ring-down cavity optimized coupling into the cavity, thus increasing the ring-down signal acquisition rate nearly 300-fold to 14 kHz and reducing the noise-equivalent absorption coefficient by more than an order of magnitude to 7 × 10−11 cm−1. We discuss how averaging approximately 1000 spectra yielded a signal-to-noise ratio of 220000. We also discuss how the spectrum frequency axis was linked to an optical frequency comb, thus enabling absolute frequency measurements of molecular optical transitions at sub-MHz levels. Applications of the spectrometer to molecular line-shape studies are also presented. For these investigations, we use semi-classical line-shape models that consider the influence of Dicke narrowing as well as the speed dependence of the pressure broadening and shifting to fit spectra. We show that the improved precision and spectrum fidelity of the spectrometer enable precise determinations of line-shape parameters. We also discuss the importance of line-shape analysis with regard to the development of new spectroscopic databases as well as in the optical determination of the Boltzmann constant