Mid-infrared quantum cascade laser based off-axis integrated cavity output spectroscopy for biogenic nitric oxide detection

Abstract

Tunable-laser absorption spectroscopy in the mid-IR spectral region is a sensitive analytical technique for trace-gas quantification. The detection of nitric oxide (NO) in exhaled breath is of particular interest in the diagnosis of lower-airway inflammation associated with a number of lung diseases and illnesses. A gas analyzer based on a continuous-wave mid-IR quantum cascade laser operating at approximately 5.2 microm and on off-axis integrated cavity output spectroscopy (ICOS) has been developed to measure NO concentrations in human breath. A compact sample cell, 5.3 cm in length and with a volume of < 80 cm3, that is suitable for on-line and off-line measurements during a single breath cycle, has been designed and tested. A noise-equivalent (signal-to-noise ratio of 1) sensitivity of 10 parts in 10(9) by volume (ppbv) of NO was achieved. The combination of ICOS with wavelength modulation resulted in a 2-ppbv noise-equivalent sensitivity. The total data acquisition and averaging time was 15 s in both cases. The feasibility of detecting NO in expired human breath as a potential noninvasive medical diagnostic tool is discussed.

Vibrational spectroscopy of biofluids for disease screening or diagnosis: translation from the laboratory to a clinical setting

“…QCL-based systems, although still quite specialized, are finding applications in medical diagnostics [74]. Because they require relatively low power and are so small, QCL-based systems may eventually replace larger and slower FTIR and other spectroscopy systems for laboratory work and may thus, with further development, have a more applicable role in a clinical-based setting.…”

Sensitivity Enhancement in Off-Axis Integrated Cavity Output Spectroscopy

“…The OA-ICOS technique has been extensively reviewed in the literature [3][4][5][6][7][8]; here we briefly highlight the most relevant aspects. It is a laser-based spectroscopic method developed from cavity ring down spectroscopy.…”

“…The development of off-axis integrated cavity output spectroscopy (OA-ICOS) [3][4][5][6][7] offered mechanical robustness and relatively simple alignment for field measurements [8], being used in numerous studies during the recent years, such as isotopic studies [9,10] and breath analysis [4,11,12]. The method can straightforward be implemented into practical trace-gas detection schemes, offering great versatility and selectivity, making it less technically demanding and more cost effective than other laser-based methods.…”

Simulation of Dicke-narrowed molecular spectra recorded by off-axis high-finesse optical cavities

“…Among the most valuable schemes, off-axis integrated-cavity-output spectroscopy (ICOS) offers several advantages. It combines the detection principle of cavity-enhanced absorption spectroscopy (CEAS) with a much simpler setup, using a multipasslike alignment for the high-finesse cavity [22][23][24][25][26]. Recently, Gupta et al have exactly reported absorption measurements of molecular hydrogen lines in Dicke-narrowing regime performed in the near infrared (8075 cm -1 ) by off-axis ICOS [27].…”