Incoherent broadband cavity enhanced absorption spectroscopy (IBBCEAS)-based strategy for direct measurement of aerosol extinction in a lidar blind zone.

In this Letter, the development of a custom-designed incoherent broadband cavity enhanced absorption spectrometer (IBBCEAS) and its application to in situ measurement of aerosol extinction near the ground surface are described in an effort to address the issue of missing data in the light detection and ranging (lidar) blind zone in the first hundreds of meters of the observation range. Combined measurements of aerosol extinction at the same location using lidar remote sensing at 355 nm and in situ IBBCEAS operating in the UV spectral region around 370 nm showed results with a good correlation (${{\rm R}^2} = {0.90}$R=0.

Analysis of the Stable Isotope Ratios (O/O, O/O, and D/H) in Glacier Water by Laser Spectrometry.

A compact isotope ratio sensor based on laser absorption spectroscopy at 2.7 μm was developed for high precision and simultaneous measurements of the D/H, O/O and O/O isotope ratios in glacier water. Measurements of the oxygen and hydrogen isotope ratios in glacier water demonstrate a 1σ precision of 0.

Circular Regression in a Dual-Phase Lock-In Amplifier for Coherent Detection of Weak Signal.

Lock-in amplification (LIA) is an effective approach for recovery of weak signal buried in noise. Determination of the input signal amplitude in a classical dual-phase LIA is based on incoherent detection which leads to a biased estimation at low signal-to-noise ratio. This article presents, for the first time to our knowledge, a new architecture of LIA involving phase estimation with a linear-circular regression for coherent detection.

High-accuracy and high-sensitivity spectroscopic measurement of dinitrogen pentoxide (NO) in an atmospheric simulation chamber using a quantum cascade laser.

A spectroscopic instrument based on a mid-infrared external cavity quantum cascade laser (EC-QCL) was developed for high-accuracy measurements of dinitrogen pentoxide (NO) at the ppbv-level. A specific concentration retrieval algorithm was developed to remove, from the broadband absorption spectrum of NO, both etalon fringes resulting from the EC-QCL intrinsic structure and spectral interference lines of HO vapour absorption, which led to a significant improvement in measurement accuracy and detection sensitivity (by a factor of 10), compared to using a traditional algorithm for gas concentration retrieval. The developed EC-QCL-based NO sensing platform was evaluated by real-time tracking NO concentration in its most important nocturnal tropospheric chemical reaction of NO + NO ↔ NO in an atmospheric simulation chamber.

Sensing atmospheric reactive species using light emitting diode by incoherent broadband cavity enhanced absorption spectroscopy.

We overview our recent progress in the developments and applications of light emitting diode-based incoherent broadband cavity enhanced absorption spectroscopy (LED-IBBCEAS) techniques for real-time optical sensing chemically reactive atmospheric species (HONO, NO, NO) in intensive campaigns and in atmospheric simulation chamber. New application of optical monitoring of NO concentration-time profile for study of the NO-initiated oxidation process of isoprene in a smog chamber is reported.