Fast, low-noise, mode-by-mode, cavity-enhanced absorption spectroscopy by diode-laser self-locking

Abstract

International audienc

Frequency-agile, rapid scanning spectroscopy

“…This technique, which we refer to as frequency-agile, rapid scanning (FARS) cavity ring-down spectroscopy, allows for ultrasensitive measurements in which the acquisition rate is limited only by the cavity response. Unlike earlier techniques [8][9][10][11]18,19 , FARS allows for spectra to be recorded without any dead time due to scanning of the laser frequency, offers a metrology-level frequency axis and utilizes a conventional Fabry-Pérot resonator rather than more unusual and cumbersome cavity configurations.This frequency stepping of the probe laser is enabled by the use of a microwave driver and a high-bandwidth electro-optic modulator (EOM) to generate a series of sidebands on the probe laser (Fig. 1).…”

“…This approach involves no mechanical motion and allows for a scanning rate of 8 kHz per cavity mode, a rate that is limited only by the cavity response time itself. Unlike rapidly frequency-swept techniques [8][9][10][11] , FARS does not reduce the measurement duty cycle, degrade the spectrum's frequency axis or require an unusual cavity configuration. FARS allows for a sensitivity of ∼2 3 10 212 cm 21 Hz 21/2 and a tuning range exceeding 70 GHz.…”

“…lasers have generally limited the use of these techniques to static or slowly varying analytes. Attempts to alleviate this limitation have relied on sweeping the laser frequency [8][9][10][11] , which can compromise the fidelity of the spectrum and the instrument sensitivity 16 and reduce the measurement duty cycle. We present a new approach for cavity ring-down spectroscopy 17 in which the laser frequency is rapidly stepped to successive resonances through the use of highbandwidth electro-optics.…”

Comparison of optical-feedback cavity-enhanced absorption spectroscopy and gas chromatography for ground-based and airborne measurements of atmospheric CO concentration

“…The most sensitive optical techniques allow a detection limit at the ppb level and below. Among them, optical-feedback cavity-enhanced absorption spectroscopy (OF-CEAS; Morville et al, 2005) exploits a high-finesse optical cavity in which a laser source is coupled to enhance the interaction of photons with gas molecules present inside the cavity (Morville et al, 2014). OF-CEAS offers many advantages for quantitative and selective trace gas analysis: it allows real-time absolute measurements with the smallest detectable absorption coefficient in the range of a few 10 −10 cm −1 for 1 s acquisition time (Landsberg et al, 2014), it does not require periodic calibrations with certified gas mixtures, its sampling volume is small (20 cm 3 ), its response time can be faster than 1 s, and it enables the development of compact instruments to be operated by nonspecialists.…”

“…The laser spectroscopy technique going under the name of OF-CEAS was introduced by Morville et al (2005) and has been further detailed in different publications (Kerstel et al, 2006;Kassi et al, 2006;Ventrillard-Courtillot et al, 2009;Faïn et al, 2014;Maignan et al, 2014;Morville et al, 2014).…”