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Instrumentation, Measurement, and Optical Sensing|75 Article(s)
All-fiber high-accuracy reconstructive spectrometer based on differential polarization division multiplexing
Junrui Liang, Jiangming Xu, Junhong He, Xiaoya Ma, Jun Ye, Jun Li, Jinyong Leng, and Pu Zhou
This study introduced a differential polarization division multiplexing (DPDM) scheme for all-fiber high-accuracy spectral measurement. Launching two orthogonal linearly polarized light beams into multimode fibers, the DPDM elegantly reconstructs the input spectra from the differential speckle, which is more comprehensive spectral-to-spatial encoding with fewer noises and better contrast. A spectral measurement with 2 pm resolution and 2000 channels was achieved. Compared with traditional transmission matrix and polarization division multiplexing schemes, the proposed DPDM approach reduced the spectral reconstruction error by 77% and 69%, respectively, offering a simple and effective solution for highly accurate spectral measurements. This study introduced a differential polarization division multiplexing (DPDM) scheme for all-fiber high-accuracy spectral measurement. Launching two orthogonal linearly polarized light beams into multimode fibers, the DPDM elegantly reconstructs the input spectra from the differential speckle, which is more comprehensive spectral-to-spatial encoding with fewer noises and better contrast. A spectral measurement with 2 pm resolution and 2000 channels was achieved. Compared with traditional transmission matrix and polarization division multiplexing schemes, the proposed DPDM approach reduced the spectral reconstruction error by 77% and 69%, respectively, offering a simple and effective solution for highly accurate spectral measurements.
Chinese Optics Letters
- Publication Date: Apr. 10, 2025
- Vol. 23, Issue 4, 041202 (2025)
4H-SiC-based soft X-ray single photon detector with linear photon energy response
Hao Qu, Weizong Xu, Jiuzhou Zhao, Dong Zhou, Fangfang Ren, Feng Zhou, Dunjun Chen, Rong Zhang, Youliao Zheng, and Hai Lu
In this work, a 4H-SiC-based soft X-ray single photon detector with photon energy resolution capability is demonstrated. The 4H-SiC p-i-n detector with an 80-μm-thick epi-layer and low intrinsic doping exhibits a low leakage current of ∼1.8 pA at -180 V, guaranteeing superior dark current performance for single photon detection with low electronic noise. An amplification strategy employing an active switch in the charge-sensitive amplifier has also been developed, where feedback-resistance-related thermal noise has been well eliminated, contributing to lower electronic noise in the amplification stage. By tuning the shaping time in the analog-to-digital circuit for precise signal processing, an optimal photon energy resolution has been achieved with a duration time within 6.4 µs, achieving an energy analysis standard deviation below 5.7%. Ultimately, superior linearity has been obtained between the output pulse amplitude and the characteristic photon energy by utilizing a series of different metal targets, opening a new opportunity for advanced soft X-ray detection technology based on wide bandgap semiconductors. In this work, a 4H-SiC-based soft X-ray single photon detector with photon energy resolution capability is demonstrated. The 4H-SiC p-i-n detector with an 80-μm-thick epi-layer and low intrinsic doping exhibits a low leakage current of ∼1.8 pA at -180 V, guaranteeing superior dark current performance for single photon detection with low electronic noise. An amplification strategy employing an active switch in the charge-sensitive amplifier has also been developed, where feedback-resistance-related thermal noise has been well eliminated, contributing to lower electronic noise in the amplification stage. By tuning the shaping time in the analog-to-digital circuit for precise signal processing, an optimal photon energy resolution has been achieved with a duration time within 6.4 µs, achieving an energy analysis standard deviation below 5.7%. Ultimately, superior linearity has been obtained between the output pulse amplitude and the characteristic photon energy by utilizing a series of different metal targets, opening a new opportunity for advanced soft X-ray detection technology based on wide bandgap semiconductors.
Chinese Optics Letters
- Publication Date: Mar. 31, 2025
- Vol. 23, Issue 3, 031202 (2025)
Keyhole morphology monitoring in laser welding using optical coherence tomography
Guanming Xie, Weixin Ma, Yueqiang Zhang, Sanhong Wang, You Li, Biao Hu, Shaohua Yan, Yu Fu, and Qifeng Yu
Optical coherence tomography (OCT) offers a direct and precise measurement of keyhole depth in laser welding, facilitating its application for quality assurance and control. Nevertheless, in high-speed welding, the keyhole lags behind the processing beam, leading to a reduction in OCT measurement accuracy. In this paper, OCT is utilized to monitor keyhole morphology by employing a scanner to deflect the measuring beam and the keyhole lag is quantitatively analyzed. Bead-on-plate welds were conducted on stainless steel and aluminum alloys at varying welding speeds. Real-time OCT data collection was performed and reconstructed to generate keyhole morphology. The aluminum alloy exhibited fluctuating keyhole morphology and irregular seam surfaces. The determination of the keyhole lag was based on the longitudinal view of keyhole morphology. Results indicated a proportional increase in keyhole lag with welding speed, and this trend was consistent for both materials. Optical coherence tomography (OCT) offers a direct and precise measurement of keyhole depth in laser welding, facilitating its application for quality assurance and control. Nevertheless, in high-speed welding, the keyhole lags behind the processing beam, leading to a reduction in OCT measurement accuracy. In this paper, OCT is utilized to monitor keyhole morphology by employing a scanner to deflect the measuring beam and the keyhole lag is quantitatively analyzed. Bead-on-plate welds were conducted on stainless steel and aluminum alloys at varying welding speeds. Real-time OCT data collection was performed and reconstructed to generate keyhole morphology. The aluminum alloy exhibited fluctuating keyhole morphology and irregular seam surfaces. The determination of the keyhole lag was based on the longitudinal view of keyhole morphology. Results indicated a proportional increase in keyhole lag with welding speed, and this trend was consistent for both materials.
Chinese Optics Letters
- Publication Date: Mar. 13, 2025
- Vol. 23, Issue 3, 031201 (2025)
Highly sensitive vector bending sensor based on chirped core fiber structure
Tian Tian, Min Li, Yiwei Ma, Song Li, Tao Geng, and Libo Yuan
It is meaningful to develop a high-performance optic bending sensor characterized by effective direction judgment, compact length, and high sensitivity. In this Letter, a compact Mach–Zehnder interferometer (MZI) fiber sensor for vector bending measurement is proposed and investigated. This sensor is prepared by off-axis splicing seven-core fibers (SCFs) and multi-mode fibers (MMFs) with different core diameters, which achieves a compact sensing length of 8 mm. The chirped core fiber structure excites the high-order cladding mode in the interference component, which enhances the sensing sensitivity. Experimental results indicate that the maximum bending sensitivity of the sensor is -230 nm/m-1. Moreover, the three bending directions of the sensor can be distinguished by judging the variations of the two interference dips during the measuring process. The proposed method and thought can provide some operating experience and principles for the all-fiber curvature sensor design. It is meaningful to develop a high-performance optic bending sensor characterized by effective direction judgment, compact length, and high sensitivity. In this Letter, a compact Mach–Zehnder interferometer (MZI) fiber sensor for vector bending measurement is proposed and investigated. This sensor is prepared by off-axis splicing seven-core fibers (SCFs) and multi-mode fibers (MMFs) with different core diameters, which achieves a compact sensing length of 8 mm. The chirped core fiber structure excites the high-order cladding mode in the interference component, which enhances the sensing sensitivity. Experimental results indicate that the maximum bending sensitivity of the sensor is -230 nm/m-1. Moreover, the three bending directions of the sensor can be distinguished by judging the variations of the two interference dips during the measuring process. The proposed method and thought can provide some operating experience and principles for the all-fiber curvature sensor design.
Chinese Optics Letters
- Publication Date: Mar. 10, 2025
- Vol. 23, Issue 2, 021204 (2025)
High-precision multichannel time-domain wavelength division multiplexing FMCW LiDAR ranging and 3D imaging|Editors' Pick
Junchen Liu, Guohao Chen, Mengxin Liu, Wanghang Gu, Taoyu Qian, Xinghua Qu, and Fumin Zhang
Accurately perceiving the multidimensional geometric information of complex equipment is crucial for improving product quality and production efficiency. We propose a multichannel time-domain wavelength division multiplexing frequency modulated continuous wave (FMCW) LiDAR integrated with the optical switch system scheme. This enables the implementation of time-domain wavelength division multiplexing technology for FMCW lasers, achieving the unified transmission of multi-length information through a single optical fiber channel. This system scheme enables parallel measurement of multiple targets and enhances the measurement accuracy of single targets by measuring the mean through multichannels, featuring versatility. In experiment, we achieved an overall absolute distance measurement accuracy better than 14 µm and individual channel accuracy better than 20 µm for non-cooperative targets at a distance of 1.3 m. The overall measurement standard deviation reached 14.73 µm, and the minimum Allan deviation was 189 nm at a 2.84 s averaging time. Additionally, we demonstrated 3D imaging experiments with “TIF” patterned cardboard and corridor stairs, obtained data precision better than 0.8 cm, and achieved high reliability in 3D imaging. Accurately perceiving the multidimensional geometric information of complex equipment is crucial for improving product quality and production efficiency. We propose a multichannel time-domain wavelength division multiplexing frequency modulated continuous wave (FMCW) LiDAR integrated with the optical switch system scheme. This enables the implementation of time-domain wavelength division multiplexing technology for FMCW lasers, achieving the unified transmission of multi-length information through a single optical fiber channel. This system scheme enables parallel measurement of multiple targets and enhances the measurement accuracy of single targets by measuring the mean through multichannels, featuring versatility. In experiment, we achieved an overall absolute distance measurement accuracy better than 14 µm and individual channel accuracy better than 20 µm for non-cooperative targets at a distance of 1.3 m. The overall measurement standard deviation reached 14.73 µm, and the minimum Allan deviation was 189 nm at a 2.84 s averaging time. Additionally, we demonstrated 3D imaging experiments with “TIF” patterned cardboard and corridor stairs, obtained data precision better than 0.8 cm, and achieved high reliability in 3D imaging.
Chinese Optics Letters
- Publication Date: Dec. 31, 2024
- Vol. 23, Issue 2, 021203 (2025)
Vibration-resistant full-field heterodyne long-arm interferometry
Qilu Jiao, Yuying Zhang, Zhou Wu, Xinxin Kong, Tong Lü, Yiwei Hao, Bo Li, and Wenxi Zhang
Long-distance surface profiling requires a high level of vibration resistance. Here, we propose a heterodyne interferometry scheme that uses two acousto-optic modulators (AOMs) to achieve precise and high-speed heterodyne phase-shifting frequencies. This solution offers high spatial resolution and effective vibration resistance. We measured the fundamental vibration conditions in the laboratory and simulated the effect of vibration on measurement repeatability across different difference frequencies. Experiments have demonstrated that this method can produce a single 3200 Hz sampling of a 1024 pixel × 1024 pixel camera within a period of 1.25 ms. The repeatability of measurements at 22 m away is better than 0.8‰ wave root mean square (RMS). Long-distance surface profiling requires a high level of vibration resistance. Here, we propose a heterodyne interferometry scheme that uses two acousto-optic modulators (AOMs) to achieve precise and high-speed heterodyne phase-shifting frequencies. This solution offers high spatial resolution and effective vibration resistance. We measured the fundamental vibration conditions in the laboratory and simulated the effect of vibration on measurement repeatability across different difference frequencies. Experiments have demonstrated that this method can produce a single 3200 Hz sampling of a 1024 pixel × 1024 pixel camera within a period of 1.25 ms. The repeatability of measurements at 22 m away is better than 0.8‰ wave root mean square (RMS).
Chinese Optics Letters
- Publication Date: Mar. 12, 2025
- Vol. 23, Issue 2, 021202 (2025)
Magnetic field search and locking scheme for all-optical single-beam atomic magnetometer
Weidong Zhang, Xiaotian Xu, Tianxiang Liao, Jingyun Fan, and Sheng-Jun Yang
Considering practical unknown magnetic detection, fast magnetic field search and locking scheme is needed in atomic magnetometers. Here, based on the in-phase response of atomic polarization rotation, we provide an iterative search and intensity-modulation feedback locking scheme for a single-beam nonlinear magneto-optical rotation (NMOR) atomic magnetometer. It takes about 0.8 s to find the unknown magnetic field with a search range of 10 to 104 nT. The measurement accuracy is within (0.2% ± 4) nT, and the 3-dB bandwidth is 87 Hz. Our scheme should be useful in cases where variations of the magnetic field cover both the weak and strong field regimes. Considering practical unknown magnetic detection, fast magnetic field search and locking scheme is needed in atomic magnetometers. Here, based on the in-phase response of atomic polarization rotation, we provide an iterative search and intensity-modulation feedback locking scheme for a single-beam nonlinear magneto-optical rotation (NMOR) atomic magnetometer. It takes about 0.8 s to find the unknown magnetic field with a search range of 10 to 104 nT. The measurement accuracy is within (0.2% ± 4) nT, and the 3-dB bandwidth is 87 Hz. Our scheme should be useful in cases where variations of the magnetic field cover both the weak and strong field regimes.
Chinese Optics Letters
- Publication Date: Feb. 28, 2025
- Vol. 23, Issue 2, 021201 (2025)
Real-time synchronous detection of wind and aerosol using a coherent lidar
Yue Shi, Xiong Luo, Peiyu Sun, Jihui Dong, Lei Tang, Jie Zhou, Ke Wang, Chunli Chen, Yunshi Wang, and Dingfu Zhou
Coherent lidar (CL) addresses existing constraints in CL data products by enabling simultaneous observation of multiple meteorological parameters such as cloud height, extinction coefficient, aerosol concentration, and wind field evaluation. A detailed analysis of CL echo signals was performed at a wavelength of 1550 nm, enabling accurate measurements of cloud height and aerosol concentration. Extensive data analyses and validation tests were conducted, aligning them with a 532 nm direct aerosol lidar (AL). The assessments of the aerosol extinction coefficient demonstrated notable consistency. This underscores the potential of advanced CL for providing prolonged and consistent observations across diverse meteorological conditions. Coherent lidar (CL) addresses existing constraints in CL data products by enabling simultaneous observation of multiple meteorological parameters such as cloud height, extinction coefficient, aerosol concentration, and wind field evaluation. A detailed analysis of CL echo signals was performed at a wavelength of 1550 nm, enabling accurate measurements of cloud height and aerosol concentration. Extensive data analyses and validation tests were conducted, aligning them with a 532 nm direct aerosol lidar (AL). The assessments of the aerosol extinction coefficient demonstrated notable consistency. This underscores the potential of advanced CL for providing prolonged and consistent observations across diverse meteorological conditions.
Chinese Optics Letters
- Publication Date: Feb. 18, 2025
- Vol. 23, Issue 1, 011203 (2025)
Simultaneous temperature and strain sensing based on a supermode interferometer
Zhifeng Wang, Jing Wen, Mengshi Zhu, Heming Wei, Liang Zhang, and Fufei Pang
A novel Mach–Zehnder interferometer (MZI) sensor based on multiple supermode interferences that can be used for dual-parameter measurements of temperature and strain is proposed and demonstrated. The MZI is made by splicing a coupled four-core sapphire-derived fiber (FSDF) between two single-mode fibers, utilizing the differences in temperature response and strain response of different supermodes in the FSDF to realize the simultaneous measurement of the two parameters. Experimental results demonstrate that the proposed MZI can achieve up to 1600 µε and 1000°C measurements with a temperature-strain cross-sensitivity of approximately 0.075°C/με. A novel Mach–Zehnder interferometer (MZI) sensor based on multiple supermode interferences that can be used for dual-parameter measurements of temperature and strain is proposed and demonstrated. The MZI is made by splicing a coupled four-core sapphire-derived fiber (FSDF) between two single-mode fibers, utilizing the differences in temperature response and strain response of different supermodes in the FSDF to realize the simultaneous measurement of the two parameters. Experimental results demonstrate that the proposed MZI can achieve up to 1600 µε and 1000°C measurements with a temperature-strain cross-sensitivity of approximately 0.075°C/με.
Chinese Optics Letters
- Publication Date: Feb. 04, 2025
- Vol. 23, Issue 1, 011202 (2025)
Temperature sensing based on Lorentz resonance and Fano resonance excited in a thin-walled SiO2 hollow microrod resonator
Binbin Yang, Zhaofeng Kang, Tianci Chen, Jun Zhang, Di Tang, Lei Zhang, Keyi Wang, and Yu Yang
A highly sensitive temperature sensor was developed using a thin-walled SiO2 hollow microrod resonator (SHMR) to excite Lorentz resonance and Fano resonance. The SHMR has a high Q factor (3.16 × 107) and concise resonance modes. Moreover, the SHMR has a small wall thickness, which can effectively improve the sensitivity of the temperature sensor. The experimental results show that the sensitivity reaches 24.78 pm/°C under Lorentz resonance and further improves to 31.28 pm/°C under Fano resonance. By further reducing the wall thickness of the SHMR, the sensitivity under Lorentz resonance is increased to 34.34 pm/°C. The sensor in this study has the advantages of low cost, simple structure, high sensitivity, and satisfactory repeatability. A highly sensitive temperature sensor was developed using a thin-walled SiO2 hollow microrod resonator (SHMR) to excite Lorentz resonance and Fano resonance. The SHMR has a high Q factor (3.16 × 107) and concise resonance modes. Moreover, the SHMR has a small wall thickness, which can effectively improve the sensitivity of the temperature sensor. The experimental results show that the sensitivity reaches 24.78 pm/°C under Lorentz resonance and further improves to 31.28 pm/°C under Fano resonance. By further reducing the wall thickness of the SHMR, the sensitivity under Lorentz resonance is increased to 34.34 pm/°C. The sensor in this study has the advantages of low cost, simple structure, high sensitivity, and satisfactory repeatability.
Chinese Optics Letters
- Publication Date: Feb. 04, 2025
- Vol. 23, Issue 1, 011201 (2025)
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