scholarly journals High Sensitivity Continuous Monitoring of Chloroform Gas by Using Wavelength Modulation Photoacoustic Spectroscopy in the Near-Infrared Range

2021 ◽  
Vol 11 (15) ◽  
pp. 6992
Author(s):  
Tie Zhang ◽  
Yuxin Xing ◽  
Gaoxuan Wang ◽  
Sailing He
Keyword(s):  
Photoacoustic Spectroscopy ◽  
Continuous Monitoring ◽  
Near Infrared ◽  
Resonant Cavity ◽  
High Sensitivity ◽  
Industrial Applications ◽  
Detection Sensitivity ◽  
Infrared Range ◽  
Wavelength Modulation ◽  
Linear Coefficient

An optical system for gaseous chloroform (CHCl3) detection based on wavelength modulation photoacoustic spectroscopy (WMPAS) is proposed for the first time by using a distributed feedback (DFB) laser with a center wavelength of 1683 nm where chloroform has strong and complex absorption peaks. The WMPAS sensor developed possesses the advantages of having a simple structure, high-sensitivity, and direct measurement. A resonant cavity made of stainless steel with a resonant frequency of 6390 Hz was utilized, and eight microphones were located at the middle of the resonator at uniform intervals to collect the sound signal. All of the devices were integrated into an instrument box for practical applications. The performance of the WMPAS sensor was experimentally demonstrated with the measurement of different concentrations of chloroform from 63 to 625 ppm. A linear coefficient R2 of 0.999 and a detection sensitivity of 0.28 ppm with a time period of 20 s were achieved at room temperature (around 20 °C) and atmosphere pressure. Long-time continuous monitoring for a fixed concentration of chloroform gas was carried out to demonstrate the excellent stability of the system. The performance of the system shows great practical value for the detection of chloroform gas in industrial applications.

scholarly journals Fracture of Be and Its Alloys - Webb Space Telescope Revisited

2021 ◽  
Author(s):  
Muhammad Musaddique Ali Rafique
Keyword(s):  
Near Infrared ◽  
Joint Venture ◽  
Coefficient Of Thermal Expansion ◽  
Infrared Range ◽  
Linear Coefficient ◽  
Space Telescope ◽  
Hexagonal Close Packed ◽  
James Webb Space Telescope ◽  
Layer Deposition ◽  
Slip Planes

NASA/ESA/CSA joint venture James Webb Space Telescope is about to be launched. It is hypothesized to operate in near-infrared range. It is also hypothesized to unveil early star formation, galaxies, and universe due to its orbit, point in orbit and orbital motion. It has been under manufacturing for over 20 years at a staggering cost of 10 billion US dollars (most expensive scientific experiment in history). Beryllium (Be) is chosen to be element for construction of its main mirrors due to its high stiffness, low density, low linear coefficient of thermal expansion (α) in cryogenics and high thermal conductivity. It is followed by gold (Au) layer deposition on its (Be) surface to enhance its sensitivity towards infrared radiation as later is hypothesized to bear superior properties. However, serious mistakes have been made in selecting this material for this application. Owing to its crystal structure (hexagonal close packed (hcp)), slip planes (basal, prismatic and pyramidal) and mechanisms of their activation, Be necessitates easy fracture at cryogenic temperature. It has anisotropic properties and prone to transverse fracture under tensile loading. Furthermore, its ductile to brittle transition temperature is very low making it entirely unsuitable for such an application. It is one of most expensive metals on planet. This study constitutes revisiting these fundamental properties and mechanisms which were entirely ignored during materials selection thus rendering whole project useless.

Trace gas detection based on photoacoustic spectroscopy in 3-D printed gas cell

2020 ◽  
Vol 28 (4) ◽  
pp. 236-242
Author(s):  
Shenlong Zha ◽  
Hongliang Ma ◽  
Changli Zha ◽  
Xueyuan Cai ◽  
Yuanyuan Li ◽  
...  
Keyword(s):  
Photoacoustic Spectroscopy ◽  
Near Infrared ◽  
Acoustic Pressure ◽  
Resonant Cavity ◽  
Photoacoustic Signal ◽  
Trace Gas ◽  
Integration Time ◽  
Photoacoustic Cell ◽  
Normal Atmospheric Pressure ◽  
Micro Resonator

A novel photoacoustic spectroscopy gas sensor based on a micro-resonator has been developed. The photoacoustic cell was designed and fabricated using 3-D printing and the photoacoustic cell volume was compressed significantly. This design greatly reduces the time of manufacturing the micro-resonator and the weight was lighter compared to traditional cells. Furthermore, the acoustic pressure distribution in the 3-D printed photoacoustic cell was analyzed by COMSOL Multiphysics software, which indicated that the strongest acoustic pressure occurred in the middle of the resonant cavity. The performance of the sensor was evaluated by detection of CH4 at normal atmospheric pressure used a near infrared distributed feedback laser emitted at 1653 nm. The characteristic of the photoacoustic signal under different pressures was also investigated. An Allan variance shows that the 3-D printed photoacoustic spectroscopy sensor has the detection limit of 1.44 ppmv (3σ) for CH4 detection at about 200 s integration time.

scholarly journals Research on Fano Resonance Sensing Characteristics Based on Racetrack Resonant Cavity

Micromachines ◽  
2021 ◽  
Vol 12 (11) ◽  
pp. 1359
Author(s):  
Yaxin Yu ◽  
Jiangong Cui ◽  
Guochang Liu ◽  
Rongyu Zhao ◽  
Min Zhu ◽  
...  
Keyword(s):  
Integrated Circuits ◽  
Fano Resonance ◽  
Near Infrared ◽  
Resonant Cavity ◽  
High Sensitivity ◽  
Infrared Region ◽  
Optical Integrated Circuits ◽  
Element Simulation ◽  
Metal Insulator Metal ◽  
Sensing Characteristics

To reduce the loss of the metal–insulator–metal waveguide structure in the near-infrared region, a plasmonic nanosensor structure based on a racetrack resonant cavity is proposed herein. Through finite element simulation, the transmission spectra of the sensor under different size parameters were analyzed, and its influence on the sensing characteristics of the system was examined. The analysis results show that the structure can excite the double Fano resonance, which has a distinctive dependence on the size parameters of the sensor. The position and line shape of the resonance peak can be adjusted by changing the key parameters. In addition, the sensor has a higher sensitivity, which can reach 1503.7 nm/RIU when being used in refractive index sensing; the figure of merit is 26.8, and it can reach 0.75 nm/°C when it is used in temperature sensing. This structure can be used in optical integrated circuits, especially high-sensitivity nanosensors.

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 Sensitivity Improvement of Extremely Low Light Scenes with RGB-NIR Multispectral Filter Array Sensor

Sensors ◽  
2019 ◽  
Vol 19 (5) ◽  
pp. 1256
Author(s):  
Seunghoon Jee ◽  
Moon Gi Kang
Keyword(s):  
Near Infrared ◽  
Signal To Noise Ratio ◽  
High Sensitivity ◽  
Color Channel ◽  
Low Light ◽  
Pixel Resolution ◽  
Edge Preserving ◽  
Linear Coefficient ◽  
Reconstruction Methods ◽  
Color Channels

Recently, several red-green-blue near-infrared (RGB-NIR) multispectral filter arrays (MFAs), which include near infrared (NIR) pixels, have been proposed. For extremely low light scenes, the RGB-NIR MFA sensor has been extended to receive NIR light, by adding NIR pixels to supplement for the insufficient visible band light energy. However, the resolution reconstruction of the RGB-NIR MFA, using demosaicing and color restoration methods, is based on the correlation between the NIR pixels and the pixels of other colors; this does not improve the RGB channel sensitivity with respect to the NIR channel sensitivity. In this paper, we propose a color restored image post-processing method to improve the sensitivity and resolution of an RGB-NIR MFA. Although several linear regression based color channel reconstruction methods have taken advantage of the high sensitivity NIR channel, it is difficult to accurately estimate the linear coefficients because of the high level of noise in the color channels under extremely low light conditions. The proposed method solves this problem in three steps: guided filtering, based on the linear similarity between the NIR and color channels, edge preserving smoothing to improve the accuracy of linear coefficient estimation, and residual compensation for lost spatial resolution information. The results show that the proposed method is effective, while maintaining the NIR pixel resolution characteristics, and improving the sensitivity in terms of the signal-to-noise ratio by approximately 13 dB.

A near-infrared C2H2/CH4 dual-gas sensor system combining off-axis integrated-cavity output spectroscopy and frequency-division-multiplexing-based wavelength modulation spectroscopy

The Analyst ◽  
2019 ◽  
Vol 144 (6) ◽  
pp. 2003-2010 ◽  
Author(s):  
Kaiyuan Zheng ◽  
Chuantao Zheng ◽  
Dan Yao ◽  
Lien Hu ◽  
Zidi Liu ◽  
...  
Keyword(s):  
Near Infrared ◽  
High Sensitivity ◽  
Dynamic Measurement ◽  
Wavelength Modulation Spectroscopy ◽  
Wavelength Modulation ◽  
Frequency Division ◽  
Modulation Spectroscopy ◽  
Cavity Output ◽  
High Finesse ◽  
High Finesse Cavity

A near-infrared C2H2/CH4 sensor was demonstrated utilizing a miniaturized high finesse cavity with high sensitivity and remarkable dynamic measurement performance.

Methods for enhancement of high-sensitivity detection for a surface wave EMAT

2021 ◽  
pp. 1-23
Author(s):  
Jin Zhang ◽  
Xin Wang ◽  
Xuebing Wang ◽  
LingLing Zheng ◽  
Ruipeng Li ◽  
...  
Keyword(s):  
Conversion Efficiency ◽  
Pulse Compression ◽  
Signal To Noise Ratio ◽  
Single Layer ◽  
High Sensitivity ◽  
Element Model ◽  
Industrial Applications ◽  
Detection Sensitivity ◽  
Electromagnetic Acoustic Transducer ◽  
Compression Technique

Due to the poor conversion efficiency and signal-to-noise ratio (SNR) of Electromagnetic Acoustic Transducer (EMAT) testing, the defect detection sensitivity is limited, which restricts the extensive industrial applications. A finite element model for the testing process of a meander-coil EMAT was established that considers the simplified excitation and detection circuits for the EMAT. Based on this model, the effect of the connection methods (parallel or series) of the coils in the generating and receiving EMATs on their generating and receiving efficiency was investigated, and the simulation results were validated experimentally. Subsequently, the pulse compression technique with a 13-bit Barker code was used for the EMAT detection, and improvements of the SNR and range resolution were established through numerical simulation and experimental measurement. The results show that compared with the traditional EMAT design, which comprises single-layer transmitting and receiving coils, the conversion efficiency of the optimized EMAT with two excitation and receiving coils in the parallel connection can be improved by 52.8%. With the application of the Barker-coded pulse compression to detect the ultrasonic A-scan signal with no synchronous average, the SNR of the defect echo can be improved by 9.5 dB compared with the A-scan signal with 128 synchronous averages.

scholarly journals A dioxaborine cyanine dye as a photoluminescence probe for sensing carbon nanotubes

2016 ◽  
Vol 7 ◽  
pp. 1991-1999 ◽  
Author(s):  
Mohammed Al Araimi ◽  
Petro Lutsyk ◽  
Anatoly Verbitsky ◽  
Yuri Piryatinski ◽  
Mykola Shandura ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Near Infrared ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
Industrial Applications ◽  
Cyanine Dye ◽  
Infrared Range ◽  
Excitation Wavelength ◽  
Potential Threat ◽  
Walled Carbon Nanotubes

The unique properties of carbon nanotubes have made them the material of choice for many current and future industrial applications. As a consequence of the increasing development of nanotechnology, carbon nanotubes show potential threat to health and environment. Therefore, development of efficient method for detection of carbon nanotubes is required. In this work, we have studied the interaction of indopentamethinedioxaborine dye (DOB-719) and single-walled carbon nanotubes (SWNTs) using absorption and photoluminescence (PL) spectroscopy. In the mixture of the dye and the SWNTs we have revealed new optical features in the spectral range of the intrinsic excitation of the dye due to resonance energy transfer from DOB-719 to SWNTs. Specifically, we have observed an emergence of new PL peaks at the excitation wavelength of 735 nm and a redshift of the intrinsic PL peaks of SWNT emission (up to 40 nm) in the near-infrared range. The possible mechanism of the interaction between DOB-719 and SWNTs has been proposed. Thus, it can be concluded that DOB-719 dye has promising applications for designing efficient and tailorable optical probes for the detection of SWNTs.

scholarly journals Applications of Near Infrared Photoacoustic Spectroscopy for Analysis of Human Respiration: A Review

Molecules ◽  
2020 ◽  
Vol 25 (7) ◽  
pp. 1728 ◽  
Author(s):  
Dan C. Dumitras ◽  
Mioara Petrus ◽  
Ana-Maria Bratu ◽  
Cristina Popa
Keyword(s):  
Photoacoustic Spectroscopy ◽  
Near Infrared ◽  
Sampling Methods ◽  
High Sensitivity ◽  
High Rate ◽  
Breath Sampling ◽  
Human Respiration ◽  
Volatile Organic ◽  
Exhaled Air ◽  
Infrared Photoacoustic Spectroscopy

In this review, applications of near-infrared photoacoustic spectroscopy are presented as an opportunity to evaluate human respiration because the measurement of breath is fast, intact and simple to implement. Recently, analytical methods for measuring biomarkers in exhaled air have been extensively developed. With laser-based photoacoustic spectroscopy, volatile organic compounds can be identified with high sensitivity, at a high rate, and with very good selectivity. The literature review has shown the applicability of near-infrared photoacoustic spectroscopy to one of the problems of the real world, i.e., human health. In addition, the review will consider and explore different breath sampling methods for human respiration analysis.

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