Higher harmonic detection employing wavelength modulation spectroscopy and near infrared diode lasers: An undergraduate experiment

2009 ◽  
Vol 77 (9) ◽  
pp. 821-825 ◽  
Author(s):  
Gottipaty Rao ◽  
Chakrapani Gudipaty ◽  
Daniel Martin
Keyword(s):  
Near Infrared ◽  
Diode Lasers ◽  
Wavelength Modulation Spectroscopy ◽  
Wavelength Modulation ◽  
Harmonic Detection ◽  
Modulation Spectroscopy ◽  
Higher Harmonic

Simultaneous Measurements of CO and CO2 Employing Wavelength Modulation Spectroscopy Using a Signal Averaging Technique at 1.578 μm

2018 ◽  
Vol 72 (9) ◽  
pp. 1380-1387 ◽  
Author(s):  
Chuanliang Li ◽  
Ligang Shao ◽  
Lijun Jiang ◽  
Xuanbing Qiu ◽  
Jilin Wei ◽  
...  
Keyword(s):  
Near Infrared ◽  
Wavelength Modulation Spectroscopy ◽  
Spectral Lines ◽  
Detection Sensitivity ◽  
Line Pair ◽  
Wavelength Modulation ◽  
Modulation Spectroscopy ◽  
Direct Absorption Spectroscopy ◽  
Allan Variation ◽  
Relationship Of

A resolved line pair was selected for simultaneous measurement of carbon monoxide (CO) and carbon dioxide (CO2) in the near-infrared (NIR) region. The spectral lines of CO and CO2 at 1.578 µm were measured by wavelength modulation spectroscopy (WMS)-2 f and the absorption was enhanced with a multipass absorption cell. The white noise was further reduced by averaging technology. The detection sensitivity (1σ) for the system is estimated at 2.63 × 10−7 cm−1 for direct absorption spectroscopy. The ultimate detection limits of CO2 and CO mixed with pure N2 at 75 Torr are 29 parts per million (ppm) and 47 ppm, respectively. It is demonstrated that the signal is highly linear with the concentration in the range of 100–800 ppm. Based on an Allan variation analysis, the minimum detectable limit of CO2 and CO is 7.5 and 14 ppm, respectively. The response time of the system is about 30 s and a relationship of temperature dependence was obtained. As an example, an in situ measurement of exhaust of alkane combustion emission is presented.

scholarly journals Development and Integration of a CO Detection System Based on Wavelength Modulation Spectroscopy Using Near-Infrared DFB Laser

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Bin Li ◽  
Shuo-Cheng Zhang ◽  
Yao-Dan Chi
Keyword(s):  
Near Infrared ◽  
Limit Of Detection ◽  
Detection System ◽  
Wavelength Modulation Spectroscopy ◽  
Detection Accuracy ◽  
Wavelength Modulation ◽  
Modulation Spectroscopy ◽  
Measure Concentration ◽  
Dfb Laser ◽  
Co Detection

A wavelength modulation spectroscopy- (WMS-) based gas sensing system was established to measure concentration of carbon monoxide (CO) in the range 0–100%. The CO absorption line at 1563.06 nm was scanned with a tunable distributed feedback (DFB) laser, and two InGaAs photodiodes were applied to perform optic-electric conversion. Without using commercial instruments, essential electrical circuits were self-developed and integrated, including laser temperature controller, laser current driver, signal generator, and digital lock-in amplifier. The gas cell deployed in the system was fiber coupled with a total effective optical path length of 50 cm. The second-order harmonic signal was extracted, and experiments of gas detection were carried out to investigate the performance of the sensor, including detection repeatability, detection accuracy, response time, and limit of detection (LoD). Experiment results show that the sensor is reliable and has acceptable probing performance. The maximum relative detection error is less than 3.8%, suggesting good detection stability. Benefiting from the self-developed sensor, the whole CO detection system has small size, affordable expense, and application potential.

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