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Instrumentation and Measurements|81 Article(s)
High-resolution miniaturized speckle spectrometry using fuse-induced fiber microvoids
Junrui Liang, Jun Li, Zhongming Huang, Junhong He, Yidong Guo, Xiaoya Ma, Yanzhao Ke, Jun Ye, Jiangming Xu, Jinyong Leng, and Pu Zhou
Miniaturized spectrometers with high resolving power and cost-effectiveness are desirable but remain an open challenge. In this work, we repurpose a fiber generated by the catastrophic fuse effect and ingeniously harness it for a speckle-based computational spectrometer. Without complex disorder engineering, the axially random micro-cavities in the fused fiber enhance the wavelength sensitivity of multimode interference, enabling a 10 cm fiber to achieve a spectral resolution of 0.1 nm. This performance exhibits sixfold improvement over a common multimode fiber configuration of the same length. Furthermore, we develop a spectral reconstruction method that combines a weighted transmission matrix with automatic differentiation, which reduces the reconstruction error by approximately half and enhances the peak signal-to-noise ratio by 6.12 dB compared to traditional Tikhonov regularization. Spectra spanning a 40 nm range, exhibiting both sparse and dense characteristics, are accurately reconstructed. To the best of our knowledge, this represents the first application of fused fiber in computational spectrometers, demonstrating its potential for a wide range of spectral measurement scenarios. Miniaturized spectrometers with high resolving power and cost-effectiveness are desirable but remain an open challenge. In this work, we repurpose a fiber generated by the catastrophic fuse effect and ingeniously harness it for a speckle-based computational spectrometer. Without complex disorder engineering, the axially random micro-cavities in the fused fiber enhance the wavelength sensitivity of multimode interference, enabling a 10 cm fiber to achieve a spectral resolution of 0.1 nm. This performance exhibits sixfold improvement over a common multimode fiber configuration of the same length. Furthermore, we develop a spectral reconstruction method that combines a weighted transmission matrix with automatic differentiation, which reduces the reconstruction error by approximately half and enhances the peak signal-to-noise ratio by 6.12 dB compared to traditional Tikhonov regularization. Spectra spanning a 40 nm range, exhibiting both sparse and dense characteristics, are accurately reconstructed. To the best of our knowledge, this represents the first application of fused fiber in computational spectrometers, demonstrating its potential for a wide range of spectral measurement scenarios.
Photonics Research
- Publication Date: Aug. 28, 2025
- Vol. 13, Issue 9, 2654 (2025)
Compact optical frequency standard using a wafer-level MEMS vapor cell
Qiaohui Yang, Zhenyu Hu, Tianyu Liu, Jie Miao, Pengyuan Chang, Duo Pan, Zhiwei Li, Xianlong Wei, and Jingbiao Chen
Atomic clocks represent the most advanced instruments for providing time-frequency standards, with increasing demand for designs that offer high frequency stability while minimizing size. Central to an atomic clock’s function is the atomic vapor cell, which serves as the quantum reference. Compared to traditional cells, wafer-level micro-electro-mechanical systems (MEMS) vapor cells enable cost-effective, scalable production and facilitate integration with silicon-based chips. In this work, we present a wafer-level MEMS vapor cell featuring an innovative silicon-glass-silicon transverse optical path structure. A single wafer is used to fabricate 24 identical atomic vapor cells, each with precise dimensions of 14 mm×14 mm×4.3 mm, ensuring scalability. We demonstrate an optical frequency standard that combines modulation transfer spectroscopy (MTS) with a MEMS vapor cell, featuring a compact design with excellent performance. This frequency standard achieves stability over averaging times of 1–400 s, with short-term stability of 2.6×10-13 at 1 s and 5.1×10-14 at 200 s. The laser linewidth is only 3.9 kHz, marking a substantial improvement over existing thermal standards, and opening potential applications in navigation, radar, and precision measurement. This work provides a crucial step toward the development of chip-scale optical clocks. Atomic clocks represent the most advanced instruments for providing time-frequency standards, with increasing demand for designs that offer high frequency stability while minimizing size. Central to an atomic clock’s function is the atomic vapor cell, which serves as the quantum reference. Compared to traditional cells, wafer-level micro-electro-mechanical systems (MEMS) vapor cells enable cost-effective, scalable production and facilitate integration with silicon-based chips. In this work, we present a wafer-level MEMS vapor cell featuring an innovative silicon-glass-silicon transverse optical path structure. A single wafer is used to fabricate 24 identical atomic vapor cells, each with precise dimensions of 14 mm×14 mm×4.3 mm, ensuring scalability. We demonstrate an optical frequency standard that combines modulation transfer spectroscopy (MTS) with a MEMS vapor cell, featuring a compact design with excellent performance. This frequency standard achieves stability over averaging times of 1–400 s, with short-term stability of 2.6×10-13 at 1 s and 5.1×10-14 at 200 s. The laser linewidth is only 3.9 kHz, marking a substantial improvement over existing thermal standards, and opening potential applications in navigation, radar, and precision measurement. This work provides a crucial step toward the development of chip-scale optical clocks.
Photonics Research
- Publication Date: Aug. 01, 2025
- Vol. 13, Issue 8, 2384 (2025)
Fourier domain mode-locked optoelectronic oscillator with an electrically tuned thin-film lithium niobate micro-ring filter|Editors' Pick
Peng Hao, Rui Ma, Zihan Shi, Zijun Huang, Ziyi Dong, Xinlun Cai, and X. Steve Yao
Linearly chirped microwave waveforms (LCMWs) are indispensable in advanced radar systems. Our study introduces and validates, through extensive experimentation, the innovative application of a thin-film lithium niobate (TFLN) photonic integrated circuit (PIC) to realize a Fourier domain mode-locked optoelectronic oscillator (FDML OEO) for generating high-precision LCMW signals. This integrated chip combines a phase modulator (PM) and an electrically tuned notch micro-ring resonator (MRR), which functions as a rapidly tunable bandpass filter, facilitating the essential phase-to-intensity modulation (PM-IM) conversion for OEO oscillation. By synchronizing the modulation period of the applied driving voltage to the MRR with the OEO loop delay, we achieve Fourier domain mode-locking, producing LCMW signals with an impressive tunable center frequency range of 18.55 GHz to 23.59 GHz, an adjustable sweep bandwidth from 3.85 GHz to 8.5 GHz, and a remarkable chirp rate up to 3.22 GHz/μs. Unlike conventional PM-IM based FDML OEOs, our device obviates the need for expensive tunable lasers or microwave sources, positioning it as a practical solution for generating high-frequency LCMW signals with extended sweep bandwidth and high chirp rates, all within a compact and cost-efficient form factor. Linearly chirped microwave waveforms (LCMWs) are indispensable in advanced radar systems. Our study introduces and validates, through extensive experimentation, the innovative application of a thin-film lithium niobate (TFLN) photonic integrated circuit (PIC) to realize a Fourier domain mode-locked optoelectronic oscillator (FDML OEO) for generating high-precision LCMW signals. This integrated chip combines a phase modulator (PM) and an electrically tuned notch micro-ring resonator (MRR), which functions as a rapidly tunable bandpass filter, facilitating the essential phase-to-intensity modulation (PM-IM) conversion for OEO oscillation. By synchronizing the modulation period of the applied driving voltage to the MRR with the OEO loop delay, we achieve Fourier domain mode-locking, producing LCMW signals with an impressive tunable center frequency range of 18.55 GHz to 23.59 GHz, an adjustable sweep bandwidth from 3.85 GHz to 8.5 GHz, and a remarkable chirp rate up to 3.22 GHz/μs. Unlike conventional PM-IM based FDML OEOs, our device obviates the need for expensive tunable lasers or microwave sources, positioning it as a practical solution for generating high-frequency LCMW signals with extended sweep bandwidth and high chirp rates, all within a compact and cost-efficient form factor.
Photonics Research
- Publication Date: Jul. 01, 2025
- Vol. 13, Issue 7, 1964 (2025)
Resonant cavity enhanced laser frequency-swept carrier ranging method for noncooperative targets
Weijin Meng, Junkang Guo, Kai Tian, Yuqi Yu, Zian Wang, Hu Peng, and Zhigang Liu
Conventional frequency-sweep interferometry is unreliable for noncooperative or long-distance targets owing to scattering on the target surface. Hence, this paper proposes a laser frequency-swept carrier (LFSC) ranging method based on resonant cavity enhancement for long-distance noncooperative target measurements and weak-signal detection. Experimental verification revealed that for a target comprising an oxidized black aluminum plate at a distance of 16 m, the standard deviation of 10 measurements was less than 70 μm, measurement accuracy exceeded 27 μm, and system ranging resolution exceeded 0.13 mm when the target feedback light was very weak. This method is useful for measurements of noncooperative targets, e.g., large-scale component assembly, industrial measurement, and biomedical testing. Conventional frequency-sweep interferometry is unreliable for noncooperative or long-distance targets owing to scattering on the target surface. Hence, this paper proposes a laser frequency-swept carrier (LFSC) ranging method based on resonant cavity enhancement for long-distance noncooperative target measurements and weak-signal detection. Experimental verification revealed that for a target comprising an oxidized black aluminum plate at a distance of 16 m, the standard deviation of 10 measurements was less than 70 μm, measurement accuracy exceeded 27 μm, and system ranging resolution exceeded 0.13 mm when the target feedback light was very weak. This method is useful for measurements of noncooperative targets, e.g., large-scale component assembly, industrial measurement, and biomedical testing.
Photonics Research
- Publication Date: Jun. 02, 2025
- Vol. 13, Issue 6, 1767 (2025)
Single-shot electro-optic sampling with arbitrary terahertz polarization
Maximilian Lenz and Pietro Musumeci
With the recent development of diversity electro-optic sampling (DEOS), significant progress has been made in the range of applicability of single-shot EOS measurements, allowing broadband THz waveforms to be captured in a single shot over large temporal windows. In addition to the decrease in acquisition time compared to standard multishot data acquisition, this technique allows measurements on systems far from equilibrium with large shot-to-shot noise or with irreversible or poorly repeatable dynamics. Although DEOS has been demonstrated and verified for linearly polarized THz waveforms, we investigate the effects resulting from the presence of a secondary polarization component. This imposes new challenges for accurate waveform reconstruction, and opens the opportunity to measure out complex polarization states such as arbitrary elliptically polarized THz field. We demonstrate a single-shot diversity-electro-optic-sampling-based approach to capture both x- and y-THz fields simultaneously with a single (110)-cut EO crystal for THz polarimetry and ellipsometry over a wide range of frequencies. With the recent development of diversity electro-optic sampling (DEOS), significant progress has been made in the range of applicability of single-shot EOS measurements, allowing broadband THz waveforms to be captured in a single shot over large temporal windows. In addition to the decrease in acquisition time compared to standard multishot data acquisition, this technique allows measurements on systems far from equilibrium with large shot-to-shot noise or with irreversible or poorly repeatable dynamics. Although DEOS has been demonstrated and verified for linearly polarized THz waveforms, we investigate the effects resulting from the presence of a secondary polarization component. This imposes new challenges for accurate waveform reconstruction, and opens the opportunity to measure out complex polarization states such as arbitrary elliptically polarized THz field. We demonstrate a single-shot diversity-electro-optic-sampling-based approach to capture both x- and y-THz fields simultaneously with a single (110)-cut EO crystal for THz polarimetry and ellipsometry over a wide range of frequencies.
Photonics Research
- Publication Date: Jun. 02, 2025
- Vol. 13, Issue 6, 1736 (2025)
Single-shot optical transfer delay measurement with sub-picosecond accuracy and sub-millisecond range
Lihan Wang, Xiangchuan Wang, Xi Liu, Yue Yang, Shupeng Li, Sihao Yang, Qianwen Sang, Zhijian Zhang, Jingxian Wang, and Shilong Pan
Optical transfer delay (OTD) is essential for distributed coherent systems, optically controlled phased arrays, fiber sensing systems, and quantum communication systems. However, existing OTD measurement techniques typically involve trade-offs among accuracy, range, and speed, limiting the application in the fields. Herein, we propose a single-shot OTD measurement approach that simultaneously achieves high-accuracy, long-range, and high-speed measurement. A microwave photonic phase-derived ranging with a nonlinear interval microwave frequency comb (MFC) and a discrete frequency sampling technique is proposed to conserve both frequency and time resources, ensuring high-accuracy and ambiguity-free measurements. In the proof-of-concept experiment, a delay measurement uncertainty at the 10-9 level with a single 10 μs sampling time is first reported, to our knowledge. The method is also applied to coherently combine two distributed signals at 31.8 GHz, separated by a 2 km optical fiber. A minimal gain loss of less than 0.0038 dB compared to the theoretical value was achieved, corresponding to an OTD synchronization accuracy of 0.3 ps. Optical transfer delay (OTD) is essential for distributed coherent systems, optically controlled phased arrays, fiber sensing systems, and quantum communication systems. However, existing OTD measurement techniques typically involve trade-offs among accuracy, range, and speed, limiting the application in the fields. Herein, we propose a single-shot OTD measurement approach that simultaneously achieves high-accuracy, long-range, and high-speed measurement. A microwave photonic phase-derived ranging with a nonlinear interval microwave frequency comb (MFC) and a discrete frequency sampling technique is proposed to conserve both frequency and time resources, ensuring high-accuracy and ambiguity-free measurements. In the proof-of-concept experiment, a delay measurement uncertainty at the 10-9 level with a single 10 μs sampling time is first reported, to our knowledge. The method is also applied to coherently combine two distributed signals at 31.8 GHz, separated by a 2 km optical fiber. A minimal gain loss of less than 0.0038 dB compared to the theoretical value was achieved, corresponding to an OTD synchronization accuracy of 0.3 ps.
Photonics Research
- Publication Date: Apr. 30, 2025
- Vol. 13, Issue 5, 1302 (2025)
Ultrafast ranging using a dispersion-controlled dual-swept laser
Wei Du, Lei Chen, Yujia Li, Jindong Wang, Yulong Cao, Ligang Huang, Leilei Shi, Lei Gao, Lei Wei, and Tao Zhu
Ranging is indispensable in a variety of fields, encompassing basic science, manufacturing, production, and daily life. Although traditional methods based on the dispersive interferometry (DPI) in the frequency domain provide high precision, their measurement speed is slow, preventing the capture and measurement of dynamic displacements. Here, we propose a fast and precise ranging method based on the dispersion-controlled dual-swept laser (DCDSL), which allows the dynamical displacement measurement of the target under test. Due to the slight frequency sweeping speed difference between the signal and reference lights, there is a zero-frequency point of the oscillation (ZPO) generated in the interference signal, whose position in the time domain is linearly related to the relative delay between the signal and reference lights. Utilizing phase demodulation of the interference signal from the DCDSL and the fitting algorithm, the time-domain position of ZPO is accurately found, which precisely maps to the displacement of the target in real time without direction ambiguity. The fast frequency sweeping rate ensures fast ranging with the MHz order refresh frame. We have experimentally demonstrated its capabilities for precise measurement of static distances and the capture of dynamic displacement processes through simulations and experiments, with the measurement range encompassing the entire interference period (56 mm). Compared to a calibrated motorized displacement platform, the residual error for full-range distance measurements is within 10 μm, and the error in average speed during dynamic processes is 0.46%. Additionally, the system exhibits excellent stability, achieving a minimum Allan deviation of 4.25 nm over an average duration of approximately 4 ms. This method ensures high precision while maintaining a simple system, thereby advancing the practical implementation of ultrafast length metrology. Ranging is indispensable in a variety of fields, encompassing basic science, manufacturing, production, and daily life. Although traditional methods based on the dispersive interferometry (DPI) in the frequency domain provide high precision, their measurement speed is slow, preventing the capture and measurement of dynamic displacements. Here, we propose a fast and precise ranging method based on the dispersion-controlled dual-swept laser (DCDSL), which allows the dynamical displacement measurement of the target under test. Due to the slight frequency sweeping speed difference between the signal and reference lights, there is a zero-frequency point of the oscillation (ZPO) generated in the interference signal, whose position in the time domain is linearly related to the relative delay between the signal and reference lights. Utilizing phase demodulation of the interference signal from the DCDSL and the fitting algorithm, the time-domain position of ZPO is accurately found, which precisely maps to the displacement of the target in real time without direction ambiguity. The fast frequency sweeping rate ensures fast ranging with the MHz order refresh frame. We have experimentally demonstrated its capabilities for precise measurement of static distances and the capture of dynamic displacement processes through simulations and experiments, with the measurement range encompassing the entire interference period (56 mm). Compared to a calibrated motorized displacement platform, the residual error for full-range distance measurements is within 10 μm, and the error in average speed during dynamic processes is 0.46%. Additionally, the system exhibits excellent stability, achieving a minimum Allan deviation of 4.25 nm over an average duration of approximately 4 ms. This method ensures high precision while maintaining a simple system, thereby advancing the practical implementation of ultrafast length metrology.
Photonics Research
- Publication Date: Apr. 21, 2025
- Vol. 13, Issue 5, 1182 (2025)
Transforming optical Vernier effect into coherent microwave interference towards highly sensitive optical fiber sensing
Ruimin Jie, Jie Huang and Chen Zhu
The optical Vernier effect has garnered significant research attention and found widespread applications in enhancing the measurement sensitivity of optical fiber interferometric sensors. Typically, Vernier sensor interrogation involves measuring its optical spectrum across a wide wavelength range using a high-precision spectrometer. This process is further complicated by the intricate signal processing required for accurately extracting the Vernier envelope, which can inadvertently introduce errors that compromise sensing performance. In this work, we introduce a novel approach to interrogating Vernier sensors based on a coherent microwave interference-assisted measurement technique. Instead of measuring the optical spectrum, we acquire the frequency response of the Vernier optical fiber sensor using a vector network analyzer. This response includes a characteristic notch that is highly sensitive to external perturbations. We discuss in detail the underlying physics of coherent microwave interference-based notch generation and the sensing principle. As a proof of concept, we construct a Vernier sensor using two air-gap Fabry–Perot interferometers arranged in parallel, demonstrating high-sensitivity strain sensing through microwave-domain measurements. The introduced technique is straightforward to implement, and the characteristic sensing signal is easy to demodulate and highly sensitive, presenting an excellent solution to the complexities of existing optical Vernier sensor systems. The optical Vernier effect has garnered significant research attention and found widespread applications in enhancing the measurement sensitivity of optical fiber interferometric sensors. Typically, Vernier sensor interrogation involves measuring its optical spectrum across a wide wavelength range using a high-precision spectrometer. This process is further complicated by the intricate signal processing required for accurately extracting the Vernier envelope, which can inadvertently introduce errors that compromise sensing performance. In this work, we introduce a novel approach to interrogating Vernier sensors based on a coherent microwave interference-assisted measurement technique. Instead of measuring the optical spectrum, we acquire the frequency response of the Vernier optical fiber sensor using a vector network analyzer. This response includes a characteristic notch that is highly sensitive to external perturbations. We discuss in detail the underlying physics of coherent microwave interference-based notch generation and the sensing principle. As a proof of concept, we construct a Vernier sensor using two air-gap Fabry–Perot interferometers arranged in parallel, demonstrating high-sensitivity strain sensing through microwave-domain measurements. The introduced technique is straightforward to implement, and the characteristic sensing signal is easy to demodulate and highly sensitive, presenting an excellent solution to the complexities of existing optical Vernier sensor systems.
Photonics Research
- Publication Date: Mar. 25, 2025
- Vol. 13, Issue 4, 875 (2025)
Turn-key Voigt optical frequency standard|On the Cover
Zijie Liu, Zhiyang Wang, Xiaomin Qin, Xiaolei Guan, Hangbo Shi, Shiying Cao, Suyang Wei, Jia Zhang, Zheng Xiao, Tiantian Shi, Anhong Dang, and Jingbiao Chen
The transportable optical clock can be deployed in various transportation vehicles, including aviation, aerospace, maritime, and land-based vehicles; provides remote time standards for geophysical monitoring and distributed coherent sensing; and promotes the unmanned and lightweight development of global time network synchronization. However, the current transportable version of laboratory optical clocks is still limited by factors such as environmental sensitivity, manual maintenance requirements, and high cost. Here we report a single-person portable optical frequency standard using the recently proposed atomic-filter-based laser “Voigt laser” as the local oscillator. It is worth mentioning that due to the inherent characteristics of Voigt lasers, the Voigt optical frequency standard can maintain turn-key functionality under harsh environmental impacts without any manual maintenance requirement. In our experiment, conducted over a duration of 12 min, we subjected the laser diode to multiple temperature shocks, resulting in a cumulative temperature fluctuation of 15°C. Following each temperature shock event, the Voigt optical frequency standard automatically relocked and restored the frequency output. Therefore, this demonstration marks a significant technological breakthrough in automatic quantum devices and might herald the arrival of fully automated time network systems. The transportable optical clock can be deployed in various transportation vehicles, including aviation, aerospace, maritime, and land-based vehicles; provides remote time standards for geophysical monitoring and distributed coherent sensing; and promotes the unmanned and lightweight development of global time network synchronization. However, the current transportable version of laboratory optical clocks is still limited by factors such as environmental sensitivity, manual maintenance requirements, and high cost. Here we report a single-person portable optical frequency standard using the recently proposed atomic-filter-based laser “Voigt laser” as the local oscillator. It is worth mentioning that due to the inherent characteristics of Voigt lasers, the Voigt optical frequency standard can maintain turn-key functionality under harsh environmental impacts without any manual maintenance requirement. In our experiment, conducted over a duration of 12 min, we subjected the laser diode to multiple temperature shocks, resulting in a cumulative temperature fluctuation of 15°C. Following each temperature shock event, the Voigt optical frequency standard automatically relocked and restored the frequency output. Therefore, this demonstration marks a significant technological breakthrough in automatic quantum devices and might herald the arrival of fully automated time network systems.
Photonics Research
- Publication Date: Apr. 01, 2025
- Vol. 13, Issue 4, 1083 (2025)
Broadband spectropolarimetry based on single-shot intensity images of polychromatic structured vector beams
Chao Gao, Xiaoyu Cao, Jianyu Weng, Bin Zhang, Dechao Liu, Yuying Mei, Xuheng Yang, Wei Liu, and Bing Lei
Broadband polarization measurement plays a crucial role in numerous fields, spanning from fundamental physics to a wide range of practical applications. However, traditional approaches typically rely on combinations of various dispersive optical elements, requiring bulky systems and complicated time-consuming multiple procedures. Here we have achieved broadband spectropolarimetry based on single-shot images for spatial intensity distributions of polychromatic vector beams. A custom-designed diffractive optical element and a vortex retarder convert the incident polychromatic waves into structured vector beams: the former diffracts light of different wavelengths into concentric circles of different radii, while the latter codes their polarization information into intensity distributions along the azimuthal direction. The validation experiments verify our exceptional measurement accuracy (RMS errors<1%) for each Stokes component in the visible light range (400–700 nm), with good spectral (<0.8 nm) and temporal (an output rate of 100 Hz) resolutions. We have further employed our broadband polarimeter to study the mutarotation of glucose, making direct observations of temporal evolutions of chemical reactions accessible. Our work has significantly broadened the toolboxes of spectropolarimetry, which can potentially incubate various disruptive applications that depend on broadband polarization measurements. Broadband polarization measurement plays a crucial role in numerous fields, spanning from fundamental physics to a wide range of practical applications. However, traditional approaches typically rely on combinations of various dispersive optical elements, requiring bulky systems and complicated time-consuming multiple procedures. Here we have achieved broadband spectropolarimetry based on single-shot images for spatial intensity distributions of polychromatic vector beams. A custom-designed diffractive optical element and a vortex retarder convert the incident polychromatic waves into structured vector beams: the former diffracts light of different wavelengths into concentric circles of different radii, while the latter codes their polarization information into intensity distributions along the azimuthal direction. The validation experiments verify our exceptional measurement accuracy (RMS errors<1%) for each Stokes component in the visible light range (400–700 nm), with good spectral (<0.8 nm) and temporal (an output rate of 100 Hz) resolutions. We have further employed our broadband polarimeter to study the mutarotation of glucose, making direct observations of temporal evolutions of chemical reactions accessible. Our work has significantly broadened the toolboxes of spectropolarimetry, which can potentially incubate various disruptive applications that depend on broadband polarization measurements.
Photonics Research
- Publication Date: Feb. 28, 2025
- Vol. 13, Issue 3, 781 (2025)
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