CW DFB RT diode laser-based sensor for trace-gas detection of ethane using a novel compact multipass gas absorption cell
CW DFB RT二极管激光传感器及新颖紧凑型多道气体吸收池在乙烷痕量气体检测中的应用
Applied Physics B, September 2013, Volume 112, Issue 4, pp 461-465
Abstract: The development of a continuous wave, thermoelectrically cooled (TEC), distributed feedback diode laser-based spectroscopic trace-gas sensor for ultra-sensitive and selective ethane (C2H6) concentration measurements is reported. The sensor platform used tunable diode laser absorption spectroscopy (TDLAS) and wavelength modulation spectroscopy as the detection technique. TDLAS was performed using an ultra-compact 57.6 m effective optical path length innovative spherical multipass cell capable of 459 passes between two mirrors separated by 12.5 cm and optimized for the 2.5–4 μm range TEC mercury–cadmium–telluride detector. For an interference-free C2H6 absorption line located at 2,976.8 cm−1, a 1σ minimum detection limit of 740 pptv with a 1 s lock-in amplifier time constant was achieved.
Characteristics of Ga and Ag-doped ZnO-based nanowires for an ethanol gas sensor prepared by hot-walled pulsed laser deposition
基于Ga与Ag掺杂ZnO及热壁脉冲激光沉积技术纳米线特性及其在乙醇气体传感器中的应用
Research on Chemical Intermediates, January 2014, Volume 40, Issue 1, pp 97-103
Abstract: Pure ZnO and Ga (3 % w/w) and Ag (3 % w/w)-doped ZnO nanowires (NWs) have been grown by use of the hot-walled pulse laser deposition technique. The doping characteristics of Ga and Ag in ZnO NWs were analyzed by use of photoluminescence (PL) and X-ray photoelectron spectroscopy (XPS) and the results were compared with those for pure ZnO NWs. We also fabricated gas sensors by use of pure ZnO and Ga and Ag-doped ZnO NWs. Among the NW sensors, the Ag-doped NW sensor was most sensitive. We synthesized the NWs on sapphire substrates under different conditions, for example temperature, time, gas flow, and distance between target and substrate. The diameter and length of NWs were <100 nm and several microns, respectively. To analyze the effect of Ag doping on ZnO NWs, we investigated the near band edge emission by use of low-temperature PL and XPS. Significant changes in resistance and sensitivity were observed. When the sensors were used at 300 °C for detection of 1 ppm ethanol vapor, the sensitivity of the pure ZnO and the Ga and Ag-doped ZnO NW gas sensors was 97, 48, and 203 %, respectively.
Mid-infrared Laser Based Gas Sensor Technologies for Environmental Monitoring, Medical Diagnostics, Industrial and Security Applications
中红外激光气体传感器技术在环境监测、医学诊断及工业安全中的应用
Terahertz and Mid Infrared Radiation: Detection of Explosives and CBRN (Using Terahertz), Part of the series NATO Science for Peace and Security Series B: Physics and Biophysics pp 153-165
Abstract: Recent advances in the development of compact sensors based on mid-infrared continuous wave (CW), thermoelectrically cooled (TEC) and room temperature operated quantum cascade lasers (QCLs) for the detection, quantification and monitoring of trace gas species and their applications in environmental and industrial process analysis will be reported. These sensors employ a 2f wavelength modulation (WM) technique based on quartz enhanced photoacoustic spectroscopy (QEPAS) that achieves detection sensitivity at the ppbv and sub ppbv concentration levels. The merits of QEPAS include an ultra-compact, rugged sensing module, with wide dynamic range and immunity to environmental acoustic noise. QCLs are convenient QEPAS excitation sources that permit the targeting of strong fundamental rotational-vibrational transitions which are one to two orders of magnitude more intense in the mid-infrared than overtone transitions in the near infrared spectral region.
CO concentration and temperature sensor for combustion gases using quantum-cascade laser absorption near 4.7 μm
基于近4.7 μm量子级联激光吸收技术的燃烧气体CO浓度与温度传感器
Applied Physics B, June 2012, Volume 107, Issue 3, pp 849-860
Abstract: A sensor for sensitive in situ measurements of carbon monoxide and temperature in combustion gases has been developed using absorption transitions in the (v′=1←v″=0) and (v′=2←v″=1) fundamental bands of CO. Recent availability of mid-infrared quantum-cascade (QC) lasers provides convenient access to the CO fundamental band near 4.7 μm, having approximately 104 and 102 times stronger absorption line-strengths compared to the overtone bands near 1.55 μm and 2.3 μm used previously to sense CO in combustion gases. Spectroscopic parameters of the selected transitions were determined via laboratory measurements in a shock tube over the 1100–2000 K range and also at room temperature. A single-laser absorption sensor was developed for accurate CO measurements in shock-heated gases by scanning the line pair v″=0, R(12) and v″=1, R(21) at 2.5 kHz. To capture the rapidly varying CO time-histories in chemical reactions, two different QC lasers were then used to probe the line-center absorbance of transitions v″=0, P(20) and v″=1, R(21) with a bandwidth of 1 MHz using fixed-wavelength direct absorption. The sensor was applied in successful shock tube measurements of temperature and CO time-histories during the pyrolysis and oxidation of methyl formate, illustrating the capability of this sensor for chemical kinetic studies.
A quartz-enhanced photoacoustic sensor for H2S trace-gas detection at 2.6 μm
2.6 μm级石英增强光声光谱传感器在H2S痕量气体检测中的应用
Applied Physics B, April 2015, Volume 119, Issue 1, pp 21-27
Abstract: We report on the realization of a quartz-enhanced photoacoustic (QEPAS) sensor for measurement of H2S gas traces. A distributed feedback diode laser working at 2.64 µm wavelength has been coupled to an acoustic detection module composed of a quartz tuning fork and a micro-resonator system, and the QEPAS signal has been optimized in terms of gas sample pressure and laser frequency modulation depth. The sensor shows a very good linearity with respect to the H2S concentration. We performed an Allan–Werle variance analysis to investigate the sensor long-term stability, and we reached a detection limit of four parts per million for 1-s integration time and 500 parts per billion in 60-s integration time. The realized QEPAS sensor represents a good compromise between performance and handiness, in view of a fully portable device.
Wireless laser spectroscopic sensor node for atmospheric CO2 monitoring—laboratory and field test
无线激光光谱传感器在大气CO2监测中的应用 --- 实验室与现场试验
Applied Physics B, February 2013, Volume 110, Issue 2, pp 241-248
Abstract: We developed a low-power, portable, wireless laser spectroscopic sensor for atmospheric CO2 monitoring. The sensor is based on tunable diode laser absorption spectroscopy with a 2-μm wavelength VCSEL as a source and wavelength modulation technique for spectroscopic signal detection. The sensor allows measurement of CO2 concentration changes with a 1σ sensitivity of 0.14 ppmv Hz−1/2. This sensor was both laboratory and field tested under varying environmental conditions. It was used to measure a soil respiration rate of topsoil in the lab and of forest floors in the field. Measurement results are compared with those of commercial non-dispersive infrared sensors and very good agreement is found.
