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Instrumentation and Measurements|73 Article(s)
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)
Toward exploring noncontinuous-state dynamics based on pulse-modulated frequency-shifted laser feedback interferometry
Jie Li, Yunkun Zhao, Jie Liu, Jianchu Liu, Hongtao Li, Qi Yu, Jialiang Lv, and Liang Lu
An exhaustive study of the noncontinuous-state laser dynamics associated with the transient optical process is significant because it reveals the complex physical mechanisms and characteristics in nonlinear laser systems. In this study, in-depth theoretical interpretation and experimental verification of the noncontinuous-state dynamics in laser system are presented, based on developed pulse-modulated frequency-shifted laser feedback interferometry (LFI). By introducing external pulse modulation, we investigate the nonlinear time-of-flight dynamics and related photon behaviors evolution of the pulsed LFI system by observing the changes in effective interference time sequences for interference realization and attainable minimum feedback photon number of the signal under various modulated noncontinuous states. Implementation of the pulse-modulated LFI scheme should exceed the pulse overlapping time window limit of 1.93 μs to effectively extract and preserve the extracavity feedback photon information. Experiments reveal that the minimum feedback photon number of signals successfully measured by the pulsed LFI sensor is 0.067 feedback photons per Doppler cycle, exhibiting high sensitivity for extremely weak signal detection. Further, simultaneous measurement for velocity and distance of the moving object is performed to validate the feasibility and applicability of the pulsed LFI. The system can successfully achieve large-range simultaneous measurements within the velocity range of 73.5-612.6 mm/s, over a distance of 25.5 km. This work opens the way to unexplored frontiers of pulsed LFI to fill the research gap in noncontinuous laser dynamics in this field, showcasing diverse and wide-ranging applications in the realm of integrated sensing, remote monitoring, and positioning and navigation. An exhaustive study of the noncontinuous-state laser dynamics associated with the transient optical process is significant because it reveals the complex physical mechanisms and characteristics in nonlinear laser systems. In this study, in-depth theoretical interpretation and experimental verification of the noncontinuous-state dynamics in laser system are presented, based on developed pulse-modulated frequency-shifted laser feedback interferometry (LFI). By introducing external pulse modulation, we investigate the nonlinear time-of-flight dynamics and related photon behaviors evolution of the pulsed LFI system by observing the changes in effective interference time sequences for interference realization and attainable minimum feedback photon number of the signal under various modulated noncontinuous states. Implementation of the pulse-modulated LFI scheme should exceed the pulse overlapping time window limit of 1.93 μs to effectively extract and preserve the extracavity feedback photon information. Experiments reveal that the minimum feedback photon number of signals successfully measured by the pulsed LFI sensor is 0.067 feedback photons per Doppler cycle, exhibiting high sensitivity for extremely weak signal detection. Further, simultaneous measurement for velocity and distance of the moving object is performed to validate the feasibility and applicability of the pulsed LFI. The system can successfully achieve large-range simultaneous measurements within the velocity range of 73.5-612.6 mm/s, over a distance of 25.5 km. This work opens the way to unexplored frontiers of pulsed LFI to fill the research gap in noncontinuous laser dynamics in this field, showcasing diverse and wide-ranging applications in the realm of integrated sensing, remote monitoring, and positioning and navigation.
Photonics Research
- Publication Date: Feb. 25, 2025
- Vol. 13, Issue 3, 671 (2025)
Chip-scale integrated optical gyroscope based on a multi-mode co-detection technique
Shuang Liu, Junyi Hu, Binjie Li, Boyi Xue, Wenjie Wan, Huilian Ma, and Zuyuan He
Gyroscopes are crucial components of inertial navigation systems, with ongoing development emphasizing miniaturization and enhanced accuracy. The recent advances in chip-scale optical gyroscopes utilizing integrated optics have attracted considerable attention, demonstrating significant advantages in achieving tactical-grade accuracy. In this paper, a new, to our knowledge, integrated optical gyroscope scheme based on the multi-mode co-detection technology is proposed, which takes the high-Q microcavity as its core sensitive element and uses the multi-mode characteristics of the microcavity to achieve the measurement of rotational angular velocity. This detection scheme breaks the tradition of optical gyroscopes based on a single mode within the sensitive ring to detect the angular rotation rate, which not only greatly simplifies the optical and electrical system of the optical gyroscope, but also has a higher detection accuracy. The gyroscope based on this detection scheme has successfully detected the Earth’s rotation on a 9.2 mm diameter microcavity with a bias instability as low as 1 deg/h, which is the best performance among the chip-scale integrated optical gyroscopes known to us. Moreover, its high dynamic range and highly simplified and reciprocal system architecture greatly enhance the feasibility of practical applications. It is anticipated that these developments will have a profound impact on the field of inertial navigation. Gyroscopes are crucial components of inertial navigation systems, with ongoing development emphasizing miniaturization and enhanced accuracy. The recent advances in chip-scale optical gyroscopes utilizing integrated optics have attracted considerable attention, demonstrating significant advantages in achieving tactical-grade accuracy. In this paper, a new, to our knowledge, integrated optical gyroscope scheme based on the multi-mode co-detection technology is proposed, which takes the high-Q microcavity as its core sensitive element and uses the multi-mode characteristics of the microcavity to achieve the measurement of rotational angular velocity. This detection scheme breaks the tradition of optical gyroscopes based on a single mode within the sensitive ring to detect the angular rotation rate, which not only greatly simplifies the optical and electrical system of the optical gyroscope, but also has a higher detection accuracy. The gyroscope based on this detection scheme has successfully detected the Earth’s rotation on a 9.2 mm diameter microcavity with a bias instability as low as 1 deg/h, which is the best performance among the chip-scale integrated optical gyroscopes known to us. Moreover, its high dynamic range and highly simplified and reciprocal system architecture greatly enhance the feasibility of practical applications. It is anticipated that these developments will have a profound impact on the field of inertial navigation.
Photonics Research
- Publication Date: Jan. 17, 2025
- Vol. 13, Issue 2, 319 (2025)
Frequency comb generation from the ultraviolet to mid-infrared region based on a three-stage cascaded PPLN chain|Editors' Pick
Xiong Qin, Daping Luo, Lian Zhou, Jiayi Pan, Zejiang Deng, Gehui Xie, Chenglin Gu, and Wenxue Li
Optical frequency combs (OFCs) have enabled significant opportunities for high-precision frequency metrology and high-resolution broadband spectroscopy. Although nonlinear photonics chips have the capacity of frequency expansion for OFCs, most of them can only access the limited bandwidths in the partial infrared region, and it is still hard to satisfy many measurement applications in the ultraviolet-to-visible region. Here, we demonstrate a compact broadband OFC scheme via the combination of three χ(2) nonlinearities in a three-stage periodically poled lithium niobate (PPLN) chain. With a supercontinuum spectrum OFC delivered into the PPLN chain, the intra-pulse diffidence frequency generation, optical parametric amplification, and high-order harmonic generation were carried out in sequence. It is crucial that the harmonics of the 1st–10th orders are simultaneously obtained with an offset-free OFC spectrum from 0.35 to 4.0 μm. In view of the great potential for integration and spectral expansion, this wideband frequency comb source will open a new insight for the valuable applications of two-dimensional material analysis, biofluorescence microscopy, and nonlinear amplitude-phase metrology. Optical frequency combs (OFCs) have enabled significant opportunities for high-precision frequency metrology and high-resolution broadband spectroscopy. Although nonlinear photonics chips have the capacity of frequency expansion for OFCs, most of them can only access the limited bandwidths in the partial infrared region, and it is still hard to satisfy many measurement applications in the ultraviolet-to-visible region. Here, we demonstrate a compact broadband OFC scheme via the combination of three χ(2) nonlinearities in a three-stage periodically poled lithium niobate (PPLN) chain. With a supercontinuum spectrum OFC delivered into the PPLN chain, the intra-pulse diffidence frequency generation, optical parametric amplification, and high-order harmonic generation were carried out in sequence. It is crucial that the harmonics of the 1st–10th orders are simultaneously obtained with an offset-free OFC spectrum from 0.35 to 4.0 μm. In view of the great potential for integration and spectral expansion, this wideband frequency comb source will open a new insight for the valuable applications of two-dimensional material analysis, biofluorescence microscopy, and nonlinear amplitude-phase metrology.
Photonics Research
- Publication Date: Aug. 29, 2024
- Vol. 12, Issue 9, 2012 (2024)
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