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Instrumentation, Measurement, and Optical Sensing|53 Article(s)
Raman signal enhancement for gas detection using a dual near-concentric cavities group
Yifan Ren, Dewang Yang, Yingxin Sun, Jiaxuan Xu, Shuofang Liu, and Yuee Chen
Effective methods are urgently required to optimize Raman spectroscopy technology to ameliorate its low detection sensitivity. Here, we superposed two near-concentric cavities to develop a dual near-concentric cavities group (DNCCG) to assess its effect on gas Raman signal intensity, signal-to-noise ratio (SNR), and limit of detection (LOD). The results showed that DNCCG generally had higher CO2 Raman signal intensity than the sum of two near-concentric cavities. Meanwhile, the noise intensity of DNCCG was not enhanced by the superposition of near-concentric cavities. Accordingly, DNCCG increased the SNR. The LOD for CO2 was 24.6 parts per million. DNCCG could be an effective method to improve the detection capability of trace gases and broaden the dynamic detection range, which might aid the future development of innovative technology for multicomponent gas detection. Effective methods are urgently required to optimize Raman spectroscopy technology to ameliorate its low detection sensitivity. Here, we superposed two near-concentric cavities to develop a dual near-concentric cavities group (DNCCG) to assess its effect on gas Raman signal intensity, signal-to-noise ratio (SNR), and limit of detection (LOD). The results showed that DNCCG generally had higher CO2 Raman signal intensity than the sum of two near-concentric cavities. Meanwhile, the noise intensity of DNCCG was not enhanced by the superposition of near-concentric cavities. Accordingly, DNCCG increased the SNR. The LOD for CO2 was 24.6 parts per million. DNCCG could be an effective method to improve the detection capability of trace gases and broaden the dynamic detection range, which might aid the future development of innovative technology for multicomponent gas detection.
Chinese Optics Letters
- Publication Date: May. 17, 2024
- Vol. 22, Issue 5, 051202 (2024)
High-precision alkali-atom density measurement and control methods using light absorption for dual-beam SERF magnetometers
Ziao Liu, Jixi Lu, Zhaohui Hu, Xiaoyu Li, Yifan Yan, Di Zhan, and Jianli Li
The alkali-atom density measurement method based on light absorption is highly suitable for a spin-exchange relaxation-free (SERF) atomic magnetometer because of its high-precision measurement and complete nonmagnetic interference. In this study, the optical rotation angle detection system based on polarization balance detection is utilized to realize the alkali-atom density real-time measurement without affecting magnetic field measurement. We discovered that there exists an optimal frequency detuning of the probe light, which offers the highest sensitivity in alkali-atom density measurement and the lowest susceptibility to temperature fluctuations in terms of the scale factor. In contrast to conventional light absorption measurements based on pump light, this method demonstrated a threefold improvement in alkali-atom density measurement sensitivity while remaining immune to ambient magnetic fields and incident light intensity fluctuations. Furthermore, we utilized this method to achieve closed-loop temperature control with an accuracy of 0.04°C. The alkali-atom density measurement method based on light absorption is highly suitable for a spin-exchange relaxation-free (SERF) atomic magnetometer because of its high-precision measurement and complete nonmagnetic interference. In this study, the optical rotation angle detection system based on polarization balance detection is utilized to realize the alkali-atom density real-time measurement without affecting magnetic field measurement. We discovered that there exists an optimal frequency detuning of the probe light, which offers the highest sensitivity in alkali-atom density measurement and the lowest susceptibility to temperature fluctuations in terms of the scale factor. In contrast to conventional light absorption measurements based on pump light, this method demonstrated a threefold improvement in alkali-atom density measurement sensitivity while remaining immune to ambient magnetic fields and incident light intensity fluctuations. Furthermore, we utilized this method to achieve closed-loop temperature control with an accuracy of 0.04°C.
Chinese Optics Letters
- Publication Date: May. 14, 2024
- Vol. 22, Issue 5, 051201 (2024)
Dynamic range expansion for optical frequency shift detection based on multiple harmonics
Yanru Zhou, Lifan Fan, Kai Xu, Wenyao Liu, Enbo Xing, Jun Tang, and Jun Liu
Sensors based on optical resonators often have their measurement range limited by their cavity linewidth, particularly in the measurement of time-varying signals. This paper introduces a method for optical frequency shift detection using multiple harmonics to expand the dynamic range of sensors based on optical resonators. The proposed method expands the measurement range of optical frequency shift beyond the cavity linewidth while maintaining measurement accuracy. The theoretical derivation of this method is carried out based on the equation of motion for an optical resonator and the recursive relationship of the Bessel function. Experimental results show that the dynamic range is expanded to 4 times greater than the conventional first harmonic method while still maintaining accuracy. Furthermore, we present an objective analysis of the correlation between the expansion factor of the method and the linewidth and free spectrum of the optical resonator. Sensors based on optical resonators often have their measurement range limited by their cavity linewidth, particularly in the measurement of time-varying signals. This paper introduces a method for optical frequency shift detection using multiple harmonics to expand the dynamic range of sensors based on optical resonators. The proposed method expands the measurement range of optical frequency shift beyond the cavity linewidth while maintaining measurement accuracy. The theoretical derivation of this method is carried out based on the equation of motion for an optical resonator and the recursive relationship of the Bessel function. Experimental results show that the dynamic range is expanded to 4 times greater than the conventional first harmonic method while still maintaining accuracy. Furthermore, we present an objective analysis of the correlation between the expansion factor of the method and the linewidth and free spectrum of the optical resonator.
Chinese Optics Letters
- Publication Date: Apr. 25, 2024
- Vol. 22, Issue 4, 041201 (2024)
Simultaneously detecting transversal and longitudinal displacement with the dielectric metasurface
Zhiyu Zhang, Chenghui Kuang, Haofeng Zang, Yonghua Lu, and Pei Wang
The compact, sensitive, and multidimensional displacement measurement device plays a crucial role in semiconductor manufacture and high-resolution optical imaging. The metasurface offers a promising solution to develop high-precision displacement metrology. In this work, we proposed and experimentally demonstrated a two-dimensional displacement (XZ) measurement device by a dielectric metasurface. Both transversal and longitudinal displacements of the metasurface can be obtained by the analysis of the interference optical intensity that is generated by the deflected light beams while the metasurface is under linearly polarized incidence. We experimentally demonstrated that displacements down to 5.4 nm along the x-axis and 0.12 µm along the z-axis can be resolved with a 900 µm × 900 µm metasurface. Our work opens up new possibilities to develop a compact high-precision multidimensional displacement sensor. The compact, sensitive, and multidimensional displacement measurement device plays a crucial role in semiconductor manufacture and high-resolution optical imaging. The metasurface offers a promising solution to develop high-precision displacement metrology. In this work, we proposed and experimentally demonstrated a two-dimensional displacement (XZ) measurement device by a dielectric metasurface. Both transversal and longitudinal displacements of the metasurface can be obtained by the analysis of the interference optical intensity that is generated by the deflected light beams while the metasurface is under linearly polarized incidence. We experimentally demonstrated that displacements down to 5.4 nm along the x-axis and 0.12 µm along the z-axis can be resolved with a 900 µm × 900 µm metasurface. Our work opens up new possibilities to develop a compact high-precision multidimensional displacement sensor.
Chinese Optics Letters
- Publication Date: Feb. 20, 2024
- Vol. 22, Issue 2, 021202 (2024)
Towards a fast and stable tachypnea monitor: a C60-Lys enabled optical fiber sensor for humidity tracking in breath progress
Fuxiang Wang, Feng Gao, Xiaoniu Wang, Ying Wang, Fei Jin, Ziqiao Ren, Jun Wu, Zhenlin Huang, Wenjun Zhou, and Changyu Shen
The pandemic of respiratory diseases enlightened people that monitoring respiration has promising prospects in averting many fatalities by tracking the development of diseases. However, the response speed of current optical fiber sensors is still insufficient to meet the requirements of high-frequency respiratory detection during respiratory failure. Here, a scheme for a fast and stable tachypnea monitor is proposed utilizing a water-soluble C60-Lys ion compound as functional material for the tracking of humidity change in the progression of breath. The polarization of C60-Lys can be tuned by the ambient relative humidity change, and an apparent refractive index alteration can be detected due to the small size effect. In our experiments, C60-Lys is conformally and uniformly deposited on the surface of a tilted fiber Bragg grating (TFBG) to fabricate an ultra-fast-response, high-sensitivity, and long-term stable optical fiber humidity sensor. A relative humidity (RH) detecting sensitivity of 0.080 dB/% RH and the equilibrium response time and recovery time of 1.85 s and 1.58 s are observed, respectively. Also, a linear relation is detected between the resonance intensity of the TFBG and the environment RH. In a practical breath monitoring experiment, the instantaneous response time and recovery time are measured as 40 ms and 41 ms, respectively, during a 1.5 Hz fast breath process. Furthermore, an excellent time stability and high repeatability are exhibited in experiments conducted over a range of 7 days. The pandemic of respiratory diseases enlightened people that monitoring respiration has promising prospects in averting many fatalities by tracking the development of diseases. However, the response speed of current optical fiber sensors is still insufficient to meet the requirements of high-frequency respiratory detection during respiratory failure. Here, a scheme for a fast and stable tachypnea monitor is proposed utilizing a water-soluble C60-Lys ion compound as functional material for the tracking of humidity change in the progression of breath. The polarization of C60-Lys can be tuned by the ambient relative humidity change, and an apparent refractive index alteration can be detected due to the small size effect. In our experiments, C60-Lys is conformally and uniformly deposited on the surface of a tilted fiber Bragg grating (TFBG) to fabricate an ultra-fast-response, high-sensitivity, and long-term stable optical fiber humidity sensor. A relative humidity (RH) detecting sensitivity of 0.080 dB/% RH and the equilibrium response time and recovery time of 1.85 s and 1.58 s are observed, respectively. Also, a linear relation is detected between the resonance intensity of the TFBG and the environment RH. In a practical breath monitoring experiment, the instantaneous response time and recovery time are measured as 40 ms and 41 ms, respectively, during a 1.5 Hz fast breath process. Furthermore, an excellent time stability and high repeatability are exhibited in experiments conducted over a range of 7 days.
Chinese Optics Letters
- Publication Date: Feb. 23, 2024
- Vol. 22, Issue 2, 021201 (2024)
High synchronization absolute distance measurement using a heterodyne and superheterodyne combined interferometer
Ziqi Yin, Fangfei Li, Yunke Sun, Yun Zou, Yan Wang, Hongxing Yang, Pengcheng Hu, Haijin Fu, and Jiubin Tan
We propose an absolute distance measurement method that employs heterodyne and superheterodyne combined interferometers to achieve synchronous detection and demodulation of multiwavelengths. Coarse and fine synthetic wavelengths are generated by a dual-longitudinal-mode He–Ne laser and four acoustic optical frequency shifters. Further, to improve phase synchronization measurement for multiwavelengths, we analyze the demodulation characteristics of coarse and fine measurement signals and adopt a demodulation method suitable for both signals. Experimental results demonstrate that the proposed method can achieve high-precision synchronous demodulation of multiwavelengths, and standard deviation is 1.7 × 10-5 m in a range of 2 m. We propose an absolute distance measurement method that employs heterodyne and superheterodyne combined interferometers to achieve synchronous detection and demodulation of multiwavelengths. Coarse and fine synthetic wavelengths are generated by a dual-longitudinal-mode He–Ne laser and four acoustic optical frequency shifters. Further, to improve phase synchronization measurement for multiwavelengths, we analyze the demodulation characteristics of coarse and fine measurement signals and adopt a demodulation method suitable for both signals. Experimental results demonstrate that the proposed method can achieve high-precision synchronous demodulation of multiwavelengths, and standard deviation is 1.7 × 10-5 m in a range of 2 m.
Chinese Optics Letters
- Publication Date: Jan. 08, 2024
- Vol. 22, Issue 1, 011204 (2024)
Welding depth measurement for different mode lasers using optical coherence tomography
Guanming Xie, Sanhong Wang, Yueqiang Zhang, You Li, Biao Hu, Yu Fu, and Qifeng Yu
Optical coherence tomography (OCT) allows a direct and precise measurement of laser welding depth by coaxially measuring the keyhole depth and can be used for process monitoring and control. When OCT measurement was taken during single-beam laser welding, the keyhole instability of aluminum welding resulted in highly scattered OCT data and complicated the welding depth extraction methods. As a combination of an inner core beam and an outer ring beam, a novel adjustable ring mode (ARM) laser for producing a stable keyhole was applied to the OCT measurement. Different ARM laser power arrangements were conducted on aluminum and copper. The results indicated that the ring beam greatly improved the stability of the core beam-induced keyhole, and smooth welding depth can be extracted from the concentrated OCT data. Optical coherence tomography (OCT) allows a direct and precise measurement of laser welding depth by coaxially measuring the keyhole depth and can be used for process monitoring and control. When OCT measurement was taken during single-beam laser welding, the keyhole instability of aluminum welding resulted in highly scattered OCT data and complicated the welding depth extraction methods. As a combination of an inner core beam and an outer ring beam, a novel adjustable ring mode (ARM) laser for producing a stable keyhole was applied to the OCT measurement. Different ARM laser power arrangements were conducted on aluminum and copper. The results indicated that the ring beam greatly improved the stability of the core beam-induced keyhole, and smooth welding depth can be extracted from the concentrated OCT data.
Chinese Optics Letters
- Publication Date: Jan. 18, 2024
- Vol. 22, Issue 1, 011203 (2024)
New speckle pattern interferometry for precise in situ deformation measurements
Ruyue Zhang, Yu Fu, and Hong Miao
A new electronic speckle pattern interferometry method is proposed to realize in situ deformation measurements. The feature of the method is the combination of a high-speed camera and multiple laser Doppler vibrometers (LDVs) for synchronous measurements. The high-speed camera is used to record and select effective interferograms, while the LDVs are used to measure the rigid body displacement caused by vibrations. A series of effective interferograms with known shifted phase values are obtained to calculate the deformation phase. The experimental results show that the method performs well in measuring static and dynamic deformations with high accuracy in vibrating environments. A new electronic speckle pattern interferometry method is proposed to realize in situ deformation measurements. The feature of the method is the combination of a high-speed camera and multiple laser Doppler vibrometers (LDVs) for synchronous measurements. The high-speed camera is used to record and select effective interferograms, while the LDVs are used to measure the rigid body displacement caused by vibrations. A series of effective interferograms with known shifted phase values are obtained to calculate the deformation phase. The experimental results show that the method performs well in measuring static and dynamic deformations with high accuracy in vibrating environments.
Chinese Optics Letters
- Publication Date: Jan. 08, 2024
- Vol. 22, Issue 1, 011202 (2024)
Simultaneous transmission of time-frequency and data with co-amplification over urban fiber links
Qian Cao, Zhou Tong, Lei Liu, Jialiang Wang, Kang Ying, Fufei Pang, and Youzhen Gui
We demonstrate a simultaneous transmission of time-frequency and data over a 160-km urban business network in Shanghai. The signals are transmitted through a cascaded optical link consisting of 48 km and 32 km, which are connected by an optical relay. The metrological signals are inserted into the communication network using dense wavelength division multiplexing. The influence of the interference between different signals has been discussed. The experimental results demonstrate that the radio frequency (RF) instability can reach 2.1×10-14 at 1 s and 2.3×10-17 at 10,000 s, and the time interval transfer of one pulse per second (1 PPS) signal with less than 10 ps at 1 s is obtained. This work paves the way for the widespread dissemination of ultra-stable time and frequency signals over the communication networks. We demonstrate a simultaneous transmission of time-frequency and data over a 160-km urban business network in Shanghai. The signals are transmitted through a cascaded optical link consisting of 48 km and 32 km, which are connected by an optical relay. The metrological signals are inserted into the communication network using dense wavelength division multiplexing. The influence of the interference between different signals has been discussed. The experimental results demonstrate that the radio frequency (RF) instability can reach 2.1×10-14 at 1 s and 2.3×10-17 at 10,000 s, and the time interval transfer of one pulse per second (1 PPS) signal with less than 10 ps at 1 s is obtained. This work paves the way for the widespread dissemination of ultra-stable time and frequency signals over the communication networks.
Chinese Optics Letters
- Publication Date: Dec. 29, 2023
- Vol. 22, Issue 1, 011201 (2024)
Improving accuracy and sensitivity of diffraction-based overlay metrology
Wenhe Yang, Nan Lin, Xin Wei, Yunyi Chen, Sikun Li, Yuxin Leng, and Jianda Shao
Overlay (OVL) for patterns placed at two different layers during microchip production is a key parameter that controls the manufacturing process. The tolerance of OVL metrology for the latest microchip needs to be at nanometer scale. This paper discusses the influence on the accuracy and sensitivity of diffraction-based overlay (DBO) after developing inspection and after etching inspection by the asymmetrical deformation of the OVL mark induced by chemical mechanical polishing or etching. We show that the accuracy and sensitivity of DBO metrology can be significantly improved by matching the measuring light wavelength to the thickness between layers and by collecting high-order diffraction signals, promising a solution for future OVL metrology equipment. Overlay (OVL) for patterns placed at two different layers during microchip production is a key parameter that controls the manufacturing process. The tolerance of OVL metrology for the latest microchip needs to be at nanometer scale. This paper discusses the influence on the accuracy and sensitivity of diffraction-based overlay (DBO) after developing inspection and after etching inspection by the asymmetrical deformation of the OVL mark induced by chemical mechanical polishing or etching. We show that the accuracy and sensitivity of DBO metrology can be significantly improved by matching the measuring light wavelength to the thickness between layers and by collecting high-order diffraction signals, promising a solution for future OVL metrology equipment.
Chinese Optics Letters
- Publication Date: Jul. 21, 2023
- Vol. 21, Issue 7, 071204 (2023)
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