Browsing by Author "Dong, Lei"
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Item Acoustic Detection Module Design of a Quartz-Enhanced Photoacoustic Sensor(MDPI, 2019) Wei, Tingting; Wu, Hongpeng; Dong, Lei; Tittel, Frank K.This review aims to discuss the latest advancements of an acoustic detection module (ADM) based on quartz-enhanced photoacoustic spectroscopy (QEPAS). Starting from guidelines for the design of an ADM, the ADM design philosophy is described. This is followed by a review of the earliest standard quartz tuning fork (QTF)-based ADM for laboratory applications. Subsequently, the design of industrial fiber-coupled and free-space ADMs based on a standard QTF for near-infrared and mid-infrared laser sources respectively are described. Furthermore, an overview of the latest development of a QEPAS ADM employing a custom QTF is reported. Numerous application examples of four QEPAS ADMs are described in order to demonstrate their reliability and robustness.Item Analysis of overtone flexural modes operation in quartz-enhanced photoacoustic spectroscopy(The Optical Society, 2016) Tittel, Frank K.; Sampaolo, Angelo; Patimisco, Pietro; Dong, Lei; Geras, Antonina; Starecki, Tomasz; Spagnolo, VincenzoA detailed investigation of a set of custom quartz tuning forks (QTFs), operating in the fundamental and first overtone flexural modes is reported. Support losses are the dominant energy dissipation processes when the QTFs vibrate at the first overtone mode. These losses can be decreased by increasing the ratio between the prong length and its thickness. The QTFs were implemented in a quartz enhanced photoacoustic spectroscopy (QEPAS) based sensor operating in the near-IR spectral range and water vapor was selected as the gas target. QTF flexural modes having the highest quality factor exhibit the largest QEPAS signal, demonstrating that, by optimizing the QTF prongs sizes, overtone modes can provide a higher QEPAS sensor performance with respect to using the fundamental mode.Item Beat frequency quartz-enhanced photoacoustic spectroscopy for fast and calibration-free continuous trace-gas monitoring(Springer Nature, 2017) Wu, Hongpeng; Dong, Lei; Zheng, Huadan; Yu, Yajun; Ma, Weiguang; Zhang, Lei; Yin, Wangbao; Xiao, Liantuan; Jia, Suotang; Tittel, Frank K.Quartz-enhanced photoacoustic spectroscopy (QEPAS) is a sensitive gas detection technique which requires frequent calibration and has a long response time. Here we report beat frequency (BF) QEPAS that can be used for ultra-sensitive calibration-free trace-gas detection and fast spectral scan applications. The resonance frequency and Q-factor of the quartz tuning fork (QTF) as well as the trace-gas concentration can be obtained simultaneously by detecting the beat frequency signal generated when the transient response signal of the QTF is demodulated at its non-resonance frequency. Hence, BF-QEPAS avoids a calibration process and permits continuous monitoring of a targeted trace gas. Three semiconductor lasers were selected as the excitation source to verify the performance of the BF-QEPAS technique. The BF-QEPAS method is capable of measuring lower trace-gas concentration levels with shorter averaging times as compared to conventional PAS and QEPAS techniques and determines the electrical QTF parameters precisely.Item Cavity-enhanced photoacoustic sensor based on a whispering-gallery-mode diode laser(Copernicus Publications, 2019) Pan, Yufeng; Dong, Lei; Wu, Hongpeng; Ma, Weiguang; Zhang, Lei; Yin, Wangbao; Xiao, Liantuan; Jia, Suotang; Tittel, Frank K.A cavity-enhanced photoacoustic (CEPA) sensor was developed based on an ultra-narrow linewidth whispering-gallery-mode (WGM) diode laser. A cavity-enhanced photoacoustic module (CEPAM) was designed to match the output beam from the WGM-diode laser, resulting in an increase in the excitation light power, which, in turn, significantly enhanced the photoacoustic signal amplitude. The results show that a signal gain factor of 166 was achieved, which is in excellent agreement with the power enhancement factor of 175 after considering the power transmissivity. The performance of the sensor was evaluated in terms of the detection sensitivity and linearity. A 1σ detection limit of 0.45 ppmV for C2H2 detection was obtained at atmospheric pressure with a 1 s averaging time.Item Compact CH4 sensor system based on a continuous-wave, low power consumption, room temperature interband cascade laser(AIP Publishing, 2016) Dong, Lei; Li, Chunguang; Sanchez, Nancy P.; Gluszek, Aleksander K.; Griffin, Robert J.; Tittel, Frank K.A tunable diode laser absorption spectroscopy-based methane sensor, employing a dense-pattern multi-pass gas cell and a 3.3 μm, CW, DFB, room temperature interband cascade laser (ICL), is reported. The optical integration based on an advanced folded optical path design and an efficient ICL control system with appropriate electrical power management resulted in a CH4 sensor with a small footprint (32 × 20 × 17 cm3) and low-power consumption (6 W). Polynomial and least-squares fit algorithms are employed to remove the baseline of the spectral scan and retrieve CH4 concentrations, respectively. An Allan-Werle deviation analysis shows that the measurement precision can reach 1.4 ppb for a 60 s averaging time. Continuous measurements covering a seven-day period were performed to demonstrate the stability and robustness of the reported CH4 sensor system.Item A compact mid-infrared dual-gas CH4/C2H6 sensor using a single interband cascade laser and custom electronics(SPIE, 2017) Ye, Weilin; Zheng, Chuantao; Tittel, Frank K.; Sanchez, Nancy P.; Gluszek, Aleksander K.; Hudzikowski, Arkadiusz J.; Lou, Minhan; Dong, Lei; Griffin, Robert J.A compact mid-infrared (MIR) dual-gas sensor system was demonstrated for simultaneous detection of methane (CH4) and ethane (C2H6) using a single continuous-wave (CW) interband cascade laser (ICL) based on tunable laser absorption spectroscopy (TDLAS) and wavelength modulation spectroscopy (WMS). Ultracompact custom electronics were developed, including a laser current driver, a temperature controller and a lock-in amplifier. These custom electronics reduce the size and weight of the sensor system as compared with a previous version based on commercial electronics. A multipass gas cell with an effective optical length of 54.6 m was employed to enhance the absorption signal. A 3337 nm ICL was capable of targeting a C2H6 absorption line at 2996.88 cm-1 and a CH4 line at 2999.06 cm-1. Dual-gas detection was realized by scanning both the CH4 and C2H6 absorption lines. Based on an Allan deviation analysis, the 1 σ minimum detection limit (MDL) was 17.4 ppbv for CH4 and 2.4 ppbv for C2H6 with an integration time of 4.3 s. TDLAS based sensor measurements for both indoor and outdoor mixing ratios of CH4 and C2H6 were conducted. The reported single ICL based dual-gas sensor system has the advantages of reduced size and cost without influencing the midinfrared sensor detection sensitivity, selectivity and reliability.Item Compact photoacoustic module for methane detection incorporating interband cascade light emitting device(The Optical Society, 2017) Zheng, Huadan; Lou, Minhan; Dong, Lei; Wu, Hongpeng; Ye, Weilin; Yin, Xukun; Kim, Chul Soo; Kim, Mijin; Bewley, William W.; Merritt, Charles D.; Canedy, Chadwick L.; Warren, Michael V.; Vurgaftman, Igor; Meyer, Jerry R.; Tittel, Frank K.A photoacoustic module (PAM) for methane detection was developed by combining a novel 3.2 μm interband cascade light emitting device (ICLED) with a compact differential photoacoustic cell. The ICLED with a 22-stage interband cascade active core emitted a collimated power of ~700 μW. A concave Al-coat reflector was positioned adjacent to the photoacoustic cell to enhance the gas absorption length. Assembly of the ICLED and reflector with the photoacoustic cell resulted in a robust and portable PAM without any moving parts. The PAM performance was evaluated in terms of operating pressure, sensitivity and linearity. A 1σ detection limit of 3.6 ppmv was achieved with a 1-s integration time.Item Compact QEPAS humidity sensor in SF6 buffer gas for high-voltage gas power systems(Elsevier, 2022) Yin, Xukun; Dong, Lei; Wu, Hongpeng; Gao, Miao; Zhang, Le; Zhang, Xueshi; Liu, Lixian; Shao, Xiaopeng; Tittel, Frank K.In SF6 insulated high-voltage gas power systems, H2O is the most problematic impurity which not only decreases insulation performance but also creates an acidic atmosphere that promotes corrosion. Corrosion damages electrical equipment and leads to leaks, which pose serious safety hazards to people and the environment. A QEPAS-based sensor system for the sub-ppm level H2O detection in SF6 buffer gas was developed by use of a near-infrared commercial DFB diode laser. Since the specific physical constants of SF6 are strongly different from that of N2 or air, the resonant frequency and Q-factor of the bare quartz tuning fork (QTF) had changed to 32,763 Hz and 4173, respectively. The optimal vertical detection position was 1.2 mm far from the QTF opening. After the experimental optimization of acoustic micro-resonator (AmR) parameters, gas pressures, and modulation depths, a detection limit of 0.49 ppm was achieved for an averaging time of 1 s, which provided a powerful prevention tool for the safety monitoring in power systems.Item Compact sound-speed sensor for quartz enhanced photoacoustic spectroscopy based applications(AIP Publishing LLC, 2015) Liu, Kun; Dong, Lei; Tittel, Frank K.A compact sound-speed sensor based on a phase difference method was developed. The sensor employs a U-shaped stainless steel tube with two holes located on its front and back ends, which serves as a sound wave guide. The phase difference between the two holes was measured using two mini-microphones by means of a phase-sensitive detection technique. This method offers the advantage of eliminating the influence of signal fluctuations. The frequency of a sound source offered by a loudspeaker can be scanned between 1 kHz and 50 kHz. The slope of the phase difference as a function of frequency was obtained by scanning the frequency of the sound source. The speed of sound was retrieved from the rate of change of the phase difference. The performance of the sensor was evaluated over a wide range of speeds of sound from 260 m/s to 1010 m/s in different gas mixtures. The measured speed of sound was found to be in good agreement with the theoretical value for the sound-speed sensor.Item Compact TDLAS based sensor design using interband cascade lasers for mid-IR trace gas sensing(The Optical Society, 2016) Dong, Lei; Tittel, Frank K.; Li, Chunguang; Sanchez, Nancy P.; Wu, Hongpeng; Zheng, Chuantao; Yu, Yajun; Sampaolo, Angelo; Griffin, Robert J.Two compact TDLAS sensor systems based on different structural optical cores were developed. The two optical cores combine two recent developments, gallium antimonide (GaSb)-based ICL and a compact multipass gas cell (MPGC) with the goal to create compact TDLAS based sensors for the mid-IR gas detection with high detection sensitivity and low power consumption. The sensors achieved minimum detection limits of ~5 ppbv and ~8 ppbv, respectively, for CH4 and C2H6 concentration measurements with a 3.7-W power consumption.Item Highly sensitive and selective CO sensor using a 2.33 μm diode laser and wavelength modulation spectroscopy(Optical Society of America, 2018) Cui, Ruyue; Dong, Lei; Wu, Hongpeng; Li, Shangzhi; Zhang, Lei; Ma, Weiguang; Yin, Wangbao; Xiao, Liantuan; Jia, Suotang; Tittel, Frank K.A ppm-level CO sensor based on a 2f wavelength modulation spectroscopy (2f-WMS) technique was developed for the application of SF6 decomposition analysis in an electric power system. A detailed investigation of the optimum target line selection was carried out to avoid spectral interference from high purity SF6 in a wide wavelength range. A diode laser emitting at 2.33 μm and a 14.5-m multipass gas cell (MGC) was employed to target the R(6) line of the CO first overtone band and increase the optical path, respectively, thus resulting in a minimum detection sensitivity of 1 ppm. A Levenberg-Marquardt nonlinear least-squares fit algorithm makes full use of the information from all data points of the 2f spectrum and as a result, a measurement precision of ~40 ppb was achieved with a data update rate of 0.6 s. The sensor performance was also evaluated in terms of the gas flow rate, stability, and linearity. The results showed that the best operating condition with a precision of 6 ppb can be achieved by increasing the gas flow rate to the value that matches the optimum averaging time of 48 s.Item Highly sensitive photoacoustic multicomponent gas sensor for SF6 decomposition online monitoring(Optical Society of America, 2019) Yin, Xukun; Dong, Lei; Wu, Hongpeng; Zhang, Lei; Ma, Weiguang; Yin, Wangbao; Xiao, Liantuan; Jia, Suotang; Tittel, Frank K.A ppb-level photoacoustic multicomponent gas sensor system for sulfur hexafluoride (SF6) decomposition detection was developed by the use of two near-infrared (NIR) diode lasers and an ultraviolet (UV) solid-state laser. A telecommunication fiber amplifier module was used to boost up the excitation optical power from the two NIR lasers. A dual-channel high-Q photoacoustic cell (PAC) was designed for the simultaneous detection of CO, H2S, and SO2 in SF6 buffer gas by means of a time division multiplexing (TDM) method. Feasibility and performance of the multicomponent sensor was evaluated, resulting in minimum detection limits of 435 ppbv, 89 ppbv, and 115 ppbv for CO, H2S, and SO2 detection at atmospheric pressure.Item Highly sensitive SO2 photoacoustic sensor for SF6decomposition detection using a compact mW-level diode-pumped solid-state laser emitting at 303 nm(The Optical Society, 2017) Yin, Xukun; Dong, Lei; Wu, Hongpeng; Zheng, Huadan; Ma, Weiguang; Zhang, Lei; Yin, Wangbao; Xiao, Liantuan; Jia, Suotang; Tittel, Frank K.A compact ppb-level SO2 photoacoustic sensor was developed for the application of SF6decomposition detection in electric power systems. The selection of the SO2 target spectrum is discussed in detail in the infrared (IR) and ultraviolet (UV) spectral regions. Based on the result of the spectrum selection, a small-sized UV-band diode-pumped solid-state laser (DPSSL) emitting at 303.6 nm with an output power of 5 mW was developed. A differential photoacoustic cell (PAC) was designed to match the output optical beam, obtain a high Q-factor and reduce the system flow noise in the SF6 buffer gas. The performance of the sensor system was assessed in terms of gas flow rate, linearity and detection sensitivity. A SO2 detection limit (1σ) of 74 ppbv was achieved with a 1-s integration time, which corresponds to a normalized noise equivalent absorption (NNEA) coefficient of 1.15 × 10−9 cm−1WHz-1/2.Item Influence of Tuning Fork Resonance Properties on Quartz-Enhanced Photoacoustic Spectroscopy Performance(MDPI, 2019) Zheng, Huadan; Lin, Haoyang; Dong, Lei; Liu, Yihua; Patimisco, Pietro; Zweck, John; Mozumder, Ali; Sampaolo, Angelo; Spagnolo, Vincenzo; Huang, Bincheng; Tang, Jieyuan; Dong, Linpeng; Zhu, Wenguo; Yu, Jianhui; Chen, Zhe; Tittel, Frank K.A detailed investigation of the influence of quartz tuning forks (QTFs) resonance properties on the performance of quartz-enhanced photoacoustic spectroscopy (QEPAS) exploiting QTFs as acousto-electric transducers is reported. The performance of two commercial QTFs with the same resonance frequency (32.7 KHz) but different geometries and two custom QTFs with lower resonance frequencies (2.9 KHz and 7.2 KHz) were compared and discussed. The results demonstrated that the fundamental resonance frequency as well as the quality factor and the electrical resistance were strongly inter-dependent on the QTF prongs geometry. Even if the resonance frequency was reduced, the quality factor must be kept as high as possible and the electrical resistance as low as possible in order to guarantee high QEPAS performance.Item Mid-infrared dual-gas sensor for simultaneous detection of methane and ethane using a single continuous-wave interband cascade laser(The Optical Society, 2016) Ye, Weilin; Li, Chunguang; Zheng, Chuantao; Sanchez, Nancy P.; Gluszek, Aleksander K.; Hudzikowski, Arkadiusz J.; Dong, Lei; Griffin, Robert J.; Tittel, Frank K.A continuous-wave (CW) interband cascade laser (ICL) based mid-infrared sensor system was demonstrated for simultaneous detection of atmospheric methane (CH4) and ethane (C2H6). A 3.337 µm CW ICL with an emitting wavenumber range of 2996.0−3001.5 cm−1 was used to simultaneously target two absorption lines, C2H6 at 2996.88 cm−1 and CH4 at 2999.06 cm−1, respectively. The sensor performance was first evaluated for single-gas detection by only targeting the absorption line of one gas species. Allan deviations of 11.2 parts per billion in volume (ppbv) for CH4 and 1.86 ppbv for C2H6 with an averaging time of 3.4 s were achieved for the detection of these two gases. Dual-gas detection was realized by using a long-term scan signal to target both CH4 and C2H6 lines. The Allan deviations increased slightly to 17.4 ppbv for CH4 and 2.4 ppbv for C2H6 with an averaging time of 4.6 s due to laser temperature and power drift caused by long-term wavelength scanning. Measurements for both indoor and outdoor concentration changes of CH4 and C2H6 were conducted. The reported single ICL based dual-gas sensor system has the advantages of reduced size and cost compared to two separate sensor systems.Item Overtone resonance enhanced single-tube on-beam quartz enhanced photoacoustic spectrophone(AIP Publishing LLC, 2016) Zheng, Huadan; Dong, Lei; Sampaolo, Angelo; Patimisco, Pietro; Ma, Weiguang; Zhang, Lei; Yin, Wangbao; Xiao, Liantuan; Spagnolo, Vincenzo; Jia, Suotang; Tittel, Frank K.A single-tube on-beam quartz enhanced photoacoustic spectroscopy (SO-QEPAS) spectrophone, which employs a custom-made quartz tuning fork (QTF) having a prong spacing of 700 μm and operating at the 1st overtone flexural mode, is reported. The design of QTF prong geometry allows the bare QTF to possess twice higher Q-factor values for the 1st overtone resonance mode falling at ∼17.7 kHz than in the fundamental resonance mode at ∼2.8 kHz, resulting in an 8 times higher QEPAS signal amplitude when operating in the 1st overtone resonance mode. Both the vertical position and length of the single-tube acoustic micro-resonator (AmR) were optimized to attain optimal spectrophone performance. Benefiting from the high overtone resonance frequency and the quasi 1st harmonic acoustic standing waves generated in the SO-QEPAS configuration, the AmR length is reduced to 14.5 mm. This allows the realization of compact spectrophone and facilitates the laser beam alignment through the QTF + AmR system. The signal enhancement in the overtone resonance mode and the high acoustic coupling efficiency between the AmR and QTF in the SO-QEPAS configuration yields an overall sensitivity enhancement factor of ∼380 with respect to the bare custom QTF operating in the fundamental resonance mode.Item Piezo-enhanced acoustic detection module for mid-infrared trace gas sensing using a grooved quartz tuning fork(Optica Publishing Group, 2019) Li, Shangzhi; Li, Shangzhi; Wu, Hongpeng; Wu, Hongpeng; Cui, Ruyue; Cui, Ruyue; Sampaolo, Angelo; Patimisco, Pietro; Spagnolo, Vincenzo; Spagnolo, Vincenzo; Spagnolo, Vincenzo; Tittel, Frank K.; Dong, Lei; Dong, LeiA grooved quartz tuning fork (QTF) with a prong spacing of 800 µm for QEPAS application is reported. The prongs spacing is large enough to facilitate optical alignments when a degraded laser beam is used for QEPAS-based trace gas sensors. The grooved QTF has a resonance frequency of 15.2 kHz at atmospheric pressure and is characterized by four rectangular grooves carved on the QTF prong surfaces. With a grooved-prong, the electrical resistance R of the QTF is reduced resulting in an enhanced piezoelectric signal, while the Q factor is not affected, remaining as high as 15000 at atmospheric pressure. The geometric parameters of the acoustic micro resonators (AmRs) for on-beam QEPAS were optimized to match the grooved QTF, and a signal-to-noise gain factor of ∼ 30 was obtained with an optimum configuration. The performance of the QEPAS-based sensor was demonstrated exploiting an interband cascade laser (ICL) for CH4 detection and a 1σ normalized noise equivalent absorption (NNEA) coefficient of 4.1×10−9 cm−1 W/√Hz was obtained at atmospheric pressure.Item Ppb-level formaldehyde detection using a CW room-temperature interband cascade laser and a miniature dense pattern multipass gas cell(The Optical Society, 2015) Dong, Lei; Yu, Yajun; Li, Chunguang; So, Stephen; Tittel, Frank K.A ppb-level formaldehyde (H2CO) sensor was developed using a thermoelectrically cooled (TEC), continuous-wave (CW) room temperature interband cascade laser (ICL) emitting at 3.59 μm and a miniature dense pattern multipass gas cell with >50 m optical path length. Performance of the sensor was investigated with two measurement schemes: direct absorption (DAS) and wavelength modulation spectroscopy (WMS). With an integration time of less than 1.5 second, a detection limit of ~3 ppbv for H2CO measurement with precision of 1.25 ppbv for DAS and 0.58 ppbv for WMS, respectively, was achieved without zero air based background subtraction. An Allan-Werle variance analysis indicated that the precisions can be further improved to 0.26 ppbv @ 300s for DAS and 69 pptv @ 90 s for WMS, respectively. A side-by-side comparison between two measurement schemes is also discussed in detail.Item Ppb-level H2S detection for SF6 decomposition based on a fiber-amplified telecommunication diode laser and a background-gas-induced high-Q photoacoustic cell(AIP Publishing, 2017) Yin, Xukun; Dong, Lei; Wu, Hongpeng; Ma, Weiguang; Zhang, Lei; Yin, Wangbao; Xiao, Liantuan; Jia, Suotang; Tittel, Frank K.A ppb-level hydrogen sulfide (H2S) gas sensor for sulfur hexafluoride (SF6) decomposition analysis was developed by means of a background-gas-induced high-Q differential photoacoustic cell (PAC) and a fiber-amplified telecommunication diode laser. The watt-level excitation laser power compensates the sensitivity loss as a result of using a low cost, near-IR laser source. The differential design with a large cylindrical resonator diameter allows the PAC to accommodate the high power beam and maintain a low noise level output. The theory of background-gas-induced high-Q PAC is provided and was verified experimentally. A H2S detection limit (1σ) of 109 ppb in a SF6 buffer gas was achieved for an averaging time of 1 s, which corresponds to a normalized noise equivalent absorption coefficient of 2.9 × 10−9 cm−1 W Hz−1/2.Item Ppbv-Level Ethane Detection Using Quartz-Enhanced Photoacoustic Spectroscopy with a Continuous-Wave, Room Temperature Interband Cascade Laser(MDPI, 2018) Li, Chunguang; Dong, Lei; Zheng, Chuantao; Lin, Jun; Wang, Yiding; Tittel, Frank K.A ppbv-level quartz-enhanced photoacoustic spectroscopy (QEPAS)-based ethane (C2H6) sensor was demonstrated by using a 3.3 μm continuous-wave (CW), distributed feedback (DFB) interband cascade laser (ICL). The ICL was employed for targeting a strong C2H6 absorption line located at 2996.88 cm−1 in its fundamental absorption band. Wavelength modulation spectroscopy (WMS) combined with the second harmonic (2f) detection technique was utilized to increase the signal-to-noise ratio (SNR) and simplify data acquisition and processing. Gas pressure and laser frequency modulation depth were optimized to be 100 Torr and 0.106 cm−1, respectively, for maximizing the 2f signal amplitude. Performance of the QEPAS sensor was evaluated using specially prepared C2H6 samples. A detection limit of 11 parts per billion in volume (ppbv) was obtained with a 1-s integration time based on an Allan-Werle variance analysis, and the detection precision can be further improved to ~1.5 ppbv by increasing the integration time up to 230 s.