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Keywords = light-induced thermoelastic spectroscopy

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16 pages, 8177 KiB  
Article
Study and Characterization of Silicon Nitride Optical Waveguide Coupling with a Quartz Tuning Fork for the Development of Integrated Sensing Platforms
by Luigi Melchiorre, Ajmal Thottoli, Artem S. Vorobev, Giansergio Menduni, Angelo Sampaolo, Giovanni Magno, Liam O’Faolain and Vincenzo Spagnolo
Sensors 2025, 25(12), 3663; https://doi.org/10.3390/s25123663 - 11 Jun 2025
Viewed by 852
Abstract
This work demonstrates an ultra-compact optical gas-sensing system, consisting of a pigtailed laser diode emitting at 1392.5 nm for water vapor (H2O) detection, a silicon nitride (Si3N4) optical waveguide to guide the laser light, and a custom-designed, [...] Read more.
This work demonstrates an ultra-compact optical gas-sensing system, consisting of a pigtailed laser diode emitting at 1392.5 nm for water vapor (H2O) detection, a silicon nitride (Si3N4) optical waveguide to guide the laser light, and a custom-designed, low-frequency, and T-shaped Quartz Tuning Fork (QTF) as the sensitive element. The system employs both Quartz-Enhanced Photoacoustic Spectroscopy (QEPAS) and Light-Induced Thermoelastic Spectroscopy (LITES) techniques for trace gas sensing. A 3.8 mm-wide, S-shaped waveguide path was designed to prevent scattered laser light from directly illuminating the QTF. Both QEPAS and LITES demonstrated comparably low signal-to-noise ratios (SNRs), ranging from 1.6 to 3.2 for a 1.6% indoor H2O concentration, primarily owing to the reduced optical power (~300 μW) delivered to the QTF excitation point. These results demonstrate the feasibility of integrating photonic devices and piezoelectric components into portable gas-sensing systems for challenging environments. Full article
(This article belongs to the Special Issue Feature Papers in Optical Sensors 2025)
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12 pages, 16116 KiB  
Article
All-Fiber LITES Sensor Based on Hollow-Core Anti-Resonant Fiber and Self-Designed Low-Frequency Quartz Tuning Fork
by Xiaorong Sun, Weipeng Chen, Ying He, Haiyue Sun, Shunda Qiao and Yufei Ma
Sensors 2025, 25(9), 2933; https://doi.org/10.3390/s25092933 - 6 May 2025
Viewed by 495
Abstract
In this paper, an all-fiber light-induced thermoelastic spectroscopy (LITES) sensor based on hollow-core anti-resonant fiber (HC-ARF) and self-designed low-frequency quartz tuning fork (QTF) is reported for the first time. By utilizing HC-ARF as both the transmission medium and gas chamber, the laser tail [...] Read more.
In this paper, an all-fiber light-induced thermoelastic spectroscopy (LITES) sensor based on hollow-core anti-resonant fiber (HC-ARF) and self-designed low-frequency quartz tuning fork (QTF) is reported for the first time. By utilizing HC-ARF as both the transmission medium and gas chamber, the laser tail fiber was spatially coupled with the HC-ARF, and the end of the HC-ARF was directly guided onto the QTF surface, resulting in an all-fiber structure. This design eliminated the need for lens combinations, thereby enhancing system stability and reducing cost and size. Additionally, a self-designed rectangular-tip QTF with a low resonant frequency of 8.69 kHz was employed to improve the sensor’s detection performance. Acetylene (C2H2), with an absorption line at 6534.37 cm−1 (1.53 μm), was chosen as the target gas. Experimental results clearly demonstrated that the detection performance of the rectangular-tip QTF system was 2.9-fold higher than that of a standard commercial QTF system. Moreover, it exhibited an outstanding linear response to varying C2H2 concentrations, indicating its high sensitivity and reliability in detecting C2H2. The Allan deviation analysis was used to assess the system’s stability, and the results indicated that the system exhibits excellent long-term stability. Full article
(This article belongs to the Special Issue Applications of Optical Sensing and Laser Spectroscopy in Gas Detection)
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14 pages, 5317 KiB  
Article
LITES-Based Sensitive CO2 Detection Using 2 μm Diode Laser and Self-Designed 9.5 kHz Quartz Tuning Fork
by Junjie Mu, Jinfeng Hou, Shaoqi Qiu, Shunda Qiao, Ying He and Yufei Ma
Sensors 2025, 25(7), 2099; https://doi.org/10.3390/s25072099 - 27 Mar 2025
Viewed by 459
Abstract
A carbon dioxide (CO2) sensor based on light-induced thermoelastic spectroscopy (LITES) using a 2 μm diode laser and a self-designed low-frequency trapezoidal-head QTF is reported for the first time in this invited paper. The self-designed trapezoidal-head QTF with a low resonant [...] Read more.
A carbon dioxide (CO2) sensor based on light-induced thermoelastic spectroscopy (LITES) using a 2 μm diode laser and a self-designed low-frequency trapezoidal-head QTF is reported for the first time in this invited paper. The self-designed trapezoidal-head QTF with a low resonant frequency of 9464.18 Hz and a high quality factor (Q) of 12,133.56 can significantly increase the accumulation time and signal level of the CO2-LITES sensor. A continuous-wave (CW) distributed-feedback (DFB) diode laser is used as the light source, and the strongest absorption line of CO2 located at 2004.01 nm is chosen. A comparison between the standard commercial QTF with the resonant frequency of 32.768 kHz and the self-designed trapezoidal-head QTF is performed. The experimental results show that the CO2-LITES sensor with the self-designed trapezoidal-head QTF has an excellent linear response to CO2 concentration, and its minimum detection limit (MDL) can reach 46.08 ppm (parts per million). When the average time is increased to 100 s based on the Allan variance analysis, the MDL of the sensor can be improved to 3.59 ppm. Compared with the 16.85 ppm of the CO2-LITES sensor with the commercial QTF, the performance is improved by 4.7 times, demonstrating the superiority of the self-designed trapezoidal-head QTF. Full article
(This article belongs to the Special Issue Sensors in 2025)
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13 pages, 9604 KiB  
Article
A Highly Sensitive Light-Induced Thermoelastic Spectroscopy Sensor Using a Charge Amplifier to Improve the Signal-to-Noise Ratio
by Hanxu Ma, Shunda Qiao, Ying He and Yufei Ma
Sensors 2025, 25(3), 946; https://doi.org/10.3390/s25030946 - 5 Feb 2025
Viewed by 795
Abstract
A highly sensitive light-induced thermoelastic spectroscopy (LITES) sensor employing a charge amplifier (CA) is reported for the first time in this invited paper. CA has the merits of high input impedance and strong anti-interference ability. The usually used transimpedance amplifier (TA) and voltage [...] Read more.
A highly sensitive light-induced thermoelastic spectroscopy (LITES) sensor employing a charge amplifier (CA) is reported for the first time in this invited paper. CA has the merits of high input impedance and strong anti-interference ability. The usually used transimpedance amplifier (TA) and voltage amplifier (VA) were also studied under the same conditions for comparison. A standard commercial quartz tuning fork (QTF) with a resonant frequency of approximately 32.76 kHz was used as the photothermal signal transducer. Methane (CH4) was used as the target gas in these sensors for performance verification. Compared to the TA-LITES sensor and VA-LITES sensor, the reported CA-LITES sensor shows improvements of 1.83 times and 5.28 times in the minimum detection limit (MDL), respectively. When compared to the LITES sensor without an amplifier (WA-LITES), the MDL has a 19.96-fold improvement. After further optimizing the gain of the CA, the MDL of the CA-LITES sensor was calculated as 2.42 ppm, which further improved the performance of the MDL by 30.3 times compared to the WA-LITES. Additionally, long-term stability is analyzed using Allan deviation analysis. When the average time of the sensor system is increased to 50 s, the MDL of the CA-LITES sensor system can be improved to 0.58 ppm. Full article
(This article belongs to the Section Optical Sensors)
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12 pages, 10559 KiB  
Article
Highly Sensitive T-Shaped Quartz Tuning Fork Based CH4-Light-Induced Thermoelastic Spectroscopy Sensor with Hydrogen and Helium Enhanced Technique
by Yuanzhi Wang, Ying He, Shunda Qiao, Xiaoming Duan and Yufei Ma
Sensors 2024, 24(23), 7743; https://doi.org/10.3390/s24237743 - 4 Dec 2024
Cited by 1 | Viewed by 1853
Abstract
In this paper, a highly sensitive methane (CH4) sensor based on light-induced thermoelastic spectroscopy (LITES) and a T-shaped quartz tuning fork (QTF) with hydrogen (H2) and helium (He) enhancement techniques are reported for the first time. The low resonant [...] Read more.
In this paper, a highly sensitive methane (CH4) sensor based on light-induced thermoelastic spectroscopy (LITES) and a T-shaped quartz tuning fork (QTF) with hydrogen (H2) and helium (He) enhancement techniques are reported for the first time. The low resonant frequency self-designed T-shaped QTF was exploited for improving the energy accumulation time. H2 and He were utilized as surrounding gases for the T-shaped QTF to minimize energy loss, thereby enhancing the sensitivity of the LITES sensor. Additionally, a fiber-coupled multi-pass cell (FC-MPC) with a 40 m optical length was utilized to improve the optical absorption of CH4. The frequency response of the T-shaped QTF with different concentrations of H2 and He was investigated, and the Q factor in the H2 and He environment increased significantly. Compared to operating QTF in a nitrogen (N2) environment, the signal amplitude was enhanced by 2.9 times and 1.9 times in pure H2 and He environments, respectively. This enhancement corresponded to a minimum detection limit (MDL) of 80.3 ppb and 113.6 ppb. Under different CH4 concentrations, the T-shaped QTF-based H2-enhanced CH4-LITES sensor showed an excellent linear response. Furthermore, through Allan deviation analysis, the MDL of the T-shaped QTF-based H2-enhanced CH4-LITES can reach 38 ppb with an 800 s integration time. Full article
(This article belongs to the Special Issue Important Achievements in Optical Measurements in China 2024–2025)
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20 pages, 5896 KiB  
Review
Recent Advances in Light-Induced Thermoelastic Spectroscopy for Gas Sensing: A Review
by Yufeng Pan, Jinbiao Zhao, Ping Lu, Chaotan Sima and Deming Liu
Remote Sens. 2023, 15(1), 69; https://doi.org/10.3390/rs15010069 - 23 Dec 2022
Cited by 16 | Viewed by 3363
Abstract
Light-induced thermoelastic spectroscopy (LITES) is a promising optical approach for gas sensing, which uses a quartz tuning fork (QTF) as a photothermal detector, instead of a commercial photodetector. Since the QTF has the advantages of low cost, small size, high resonance frequency, high-quality [...] Read more.
Light-induced thermoelastic spectroscopy (LITES) is a promising optical approach for gas sensing, which uses a quartz tuning fork (QTF) as a photothermal detector, instead of a commercial photodetector. Since the QTF has the advantages of low cost, small size, high resonance frequency, high-quality factor (Q-factor), and a wide spectral response range, and the LITES sensor has received extensive attention and obtained great development. This review paper summarizes and discusses the advances of the QTF-based, state-of-the-art LITES gas sensing technique in recent years and presents the development prospects of LITES sensor in the future. Full article
(This article belongs to the Special Issue Development and Application for Laser Spectroscopies)
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8 pages, 1620 KiB  
Communication
Highly Sensitive Trace Gas Detection Based on In-Plane Single-Quartz-Enhanced Dual Spectroscopy
by Tiantian Liang, Shunda Qiao, Ziting Lang and Yufei Ma
Sensors 2022, 22(3), 1035; https://doi.org/10.3390/s22031035 - 28 Jan 2022
Cited by 8 | Viewed by 2962
Abstract
For this invited manuscript, an in-plane single-quartz-enhanced dual spectroscopy (IP-SQEDS)-based trace gas sensor was demonstrated for the first time. A single quartz tuning fork (QTF) was employed to combine in-plane quartz-enhanced photoacoustic spectroscopy (IP-QEPAS) with light-induced thermoelastic spectroscopy (LITES) techniques. Water vapor (H [...] Read more.
For this invited manuscript, an in-plane single-quartz-enhanced dual spectroscopy (IP-SQEDS)-based trace gas sensor was demonstrated for the first time. A single quartz tuning fork (QTF) was employed to combine in-plane quartz-enhanced photoacoustic spectroscopy (IP-QEPAS) with light-induced thermoelastic spectroscopy (LITES) techniques. Water vapor (H2O) was chosen as the target gas. Compared to traditional QEPAS, IP-SQEDS not only allowed for simple structures, but also obtained nearly three times signal amplitude enhancement. Full article
(This article belongs to the Special Issue Feature Papers in Optical Sensors 2022)
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8 pages, 21968 KiB  
Communication
Ultra-Highly Sensitive Ammonia Detection Based on Light-Induced Thermoelastic Spectroscopy
by Yao Mi and Yufei Ma
Sensors 2021, 21(13), 4548; https://doi.org/10.3390/s21134548 - 2 Jul 2021
Cited by 13 | Viewed by 2772
Abstract
This invited paper demonstrated an ultra-highly sensitive ammonia (NH3) sensor based on the light-induced thermoelastic spectroscopy (LITES) technique for the first time. A quartz tuning fork (QTF) with a resonance frequency of 32.768 kHz was employed as a detector. A fiber-coupled, [...] Read more.
This invited paper demonstrated an ultra-highly sensitive ammonia (NH3) sensor based on the light-induced thermoelastic spectroscopy (LITES) technique for the first time. A quartz tuning fork (QTF) with a resonance frequency of 32.768 kHz was employed as a detector. A fiber-coupled, continuous wave (CW), distributed feedback (DFB) diode laser emitting at 1530.33 nm was chosen as the excitation source. Wavelength modulation spectroscopy (WMS) and second-harmonic (2f) detection techniques were applied to reduce the background noise. In a one scan period, a 2f signal of the two absorption lines located at 6534.6 cm−1 and 6533.4 cm−1 were acquired simultaneously. The 2f signal amplitude at the two absorption lines was proved to be proportional to the concentration, respectively, by changing the concentration of NH3 in the analyte. The calculated R-square values of the linear fit are equal to ~0.99. The wavelength modulation depth was optimized to be 13.38 mA, and a minimum detection limit (MDL) of ~5.85 ppm was achieved for the reported NH3 sensor. Full article
(This article belongs to the Special Issue Advanced Fiber Photonic Devices and Sensors)
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