Cavity ringdown spectroscopic detection of nitric oxide with a continuous-wave quantum-cascade laser

Abstract

A spectroscopic gas sensor for nitric oxide (NO) detection based on a cavity ringdown technique was designed and evaluated. A cw quantum-cascade distributed-feedback laser operating at 5.2 mum was used as a tunable single-frequency light source. Both laser-frequency tuning and abrupt interruptions of the laser radiation were performed through manipulation of the laser current. A single ringdown event sensitivity to absorption of 2.2 x 10(-8) cm(-1) was achieved. Measurements of parts per billion (ppb) NO concentrations in N(2) with a 0.7-ppb standard error for a data collection time of 8 s have been performed. Future improvements are discussed that would allow quantification of NO in human breath.

Sub-part-per-billion monitoring of nitric oxide by use of wavelength modulation spectroscopy in combination with a thermoelectrically cooled, continuous-wave quantum cascade laser

“…The sensitivity achieved here is limited mainly by residual interference between optical elements. Our detection limit for NO of 0.2 ppbv over 30 s can be compared with previous results of 0.12 ppbv Hz −1/2 obtained using a 210 m path length and temporal gating of signal and reference laser pulses on the detector, 12 41 ppbv at 25 mbars using Faraday modulation spectroscopy, 13 0.7 ppbv over 8 s at 80 mbars using cw cavity ringdown spectroscopy, 6 and 1 ppbv for CO-laser based photoacoustics.…”

“…These include frequency modulation spectroscopy, 3 direct absorption spectroscopy using long-path multipass cells, 4 photoacoustic spectroscopy, 5 cavity ringdown spectroscopy, 6 cavityenhanced absorption spectroscopy, 4 and off-axis integrated cavity output spectroscopy. [7][8][9] Only recently, cw QCLs that are able to operate in single mode at room temperature have become available.…”

Cavity-enhanced optical frequency comb spectroscopy: application to human breath analysis

“…Several methods of trace molecular detection have been applied to the problem of breath analysis, including optical detection 3,4 , mass spectrometry 5,6 , and electronic noses 6,7 . To understand the choice of optical detection as the preferred technique for breath analysis, we first evaluate the available techniques in the context of the system criteria.…”

“…While these hybrid systems are highly sensitive and accurate for a large number of biomarkers, they are also large, complex, and require a long period of time to perform a measurement 8 . 3 These lasers are also used to detect nitric oxide for diagnosing asthma 4 . Finally, both quantum cascade and lead salt lasers have been used to detect ethane which is produced in lipid peroxidation and by some forms of cancer 12,13,14 .…”

Spectroscopic monitoring of NO traces in plants and human breath: applications and perspectives

“…QCLs emitting in the NO fundamental vibration-rotation band (centred at 5.2 µm) have in recent years triggered the development of QCL-based NO sensors using various spectroscopic methods including direct absorption spectroscopy using multi-pass cells [12], wavelength modulation spectroscopy [13], photoacoustic spectroscopy [14], FRS [15] and high-finesse cavities for extreme absorption path length, i.e. cavity ring-down spectroscopy and on/off-axis integrated cavity output spectroscopy [16,17].…”