2023

• Record 457 of
  
  Title:Super-resolution reconstruction of structured illumination microscopy based on pixel reassignment
  
  Author(s):Liu, Xing(1,2,3); Fang, Xiang(1,2,3); Lei, Yunze(1,2,3); Li, Jiaoyue(1,2,3); An, Sha(1,2,3); Zheng, Juanjuan(1,2,3,4); Ma, Ying(1,2,3); Ma, Haiyang(1,2,3); Zalevsky, Zeev(5); Gao, Peng(1,2,3)
  Source: Applied Physics Letters  Volume: 123  Issue: 13  Article Number: 131111  DOI: 10.1063/5.0162381  Published: September 25, 2023  
  Abstract:In this work, we report a pixel reassignment based super-resolution reconstruction algorithm for structured illumination microscopy (entitled PR-SIM). PR-SIM provides a twofold theoretical resolution enhancement by reassigning the pixels in raw SIM images with respect to the center of each illumination fringe and applying further deconvolution. By comparing with frequency domain based algorithms, PR-SIM is more immune to fringe distortion and, hence, it is more suited for large-field SIM in that it processes the raw images locally. Meanwhile, the reconstruction speed of PR-SIM can be enhanced by skipping empty regions in the image and further enhanced by employing GPU-base parallel calculation. Overall, we can envisage that the PR-SIM can be extended for other illumination modulation based microscopic techniques. © 2023 Author(s).
  Accession Number: 20234014842785
• Record 458 of
  
  Title:3-D Imaging Lidar Based on Miniaturized Streak Tube
  
  Author(s):Tian, Liping(1,2); Shen, Lingbin(1); Xue, Yanhua(2); Chen, Lin(1); Chen, Ping(2); Tian, Jinshou(2); Zhao, Wei(2)
  Source: Measurement Science Review  Volume: 23  Issue: 2  Article Number: null  DOI: 10.2478/msr-2023-0010  Published: April 1, 2023  
  Abstract:Streak Tube Imaging Lidar (STIL), with advantages of non-scanning working mode, small distortion, high image framing rate, high resolution in low contrast environment, compact structure, easy miniaturization and high reliability, has a wide range of applications in military, aerospace, space confrontation, attack and defense, and marine law enforcement. This article introduces the principle of single-slit and multi-slit streak tube imaging lidar. It also introduces a single-slit general streak camera that can be used for imaging lidar. In addition, a multi-slit miniaturized streak tube with a single-lens focusing system with a total length of about 200 mm has been designed. The results of the 3D electromagnetic simulation show that the effective photocathode area of this streak tube reaches 36 mm × 36 mm, the temporal resolution is better than 50 ps, the dynamic spatial resolution can reach 12 lp/mm, and the whole photocathode can accommodate at least 19 slits in the effective detection range. The streak tube has a meshless structure, which is highly reliable. The streak tube can be used to increase the field of view of the imaging lidar system, improve the reliability, and achieve system miniaturization. © 2023 Liping Tian et al., published by Sciendo.
  Accession Number: 20231914077042
• Record 459 of
  
  Title:Optical remote imaging via Fourier ptychography
  
  Author(s):Tian, Zhiming(1); Zhao, Ming(1); Yang, Dong(2); Wang, Sen(1); Pan, An(3,4)
  Source: Photonics Research  Volume: 11  Issue: 12  Article Number: null  DOI: 10.1364/PRJ.493938  Published: December 2023  
  Abstract:Combining the synthetic aperture radar (SAR) with the optical phase recovery, Fourier ptychography (FP) can be a promising technique for high-resolution optical remote imaging. However, there are still two issues that need to be addressed. First, the multi-angle coherent model of FP would be destroyed by the diffuse object; whether it can improve the resolution or just suppress the speckle is unclear. Second, the imaging distance is in meter scale and the diameter of field of view (FOV) is around centimeter scale, which greatly limits the application. In this paper, the reasons for the limitation of distance and FOV are analyzed, which mainly lie in the illumination scheme. We report a spherical wave illumination scheme and its algorithm to obtain larger FOV and longer distance. A noise suppression algorithm is reported to improve the reconstruction quality. The theoretical interpretation of our system under random phase is given. It is confirmed that FP can improve the resolution to the theoretical limit of the virtual synthetic aperture rather than simply suppressing the speckle. A 10 m standoff distance experiment with a six-fold synthetic aperture up to 31 mm over an object of size ∼1 m× 0.7 m is demonstrated. ©2023 Chinese Laser Press.
  Accession Number: 20234915184097
• Record 460 of
  
  Title:Single-Mode Single-Polarization Chalcogenide Negative-Curvature Hollow-Core Fibers at 4 μm
  
  Author(s):Ma, Xinxin(1); Li, Jianshe(1); Guo, Haitao(2); Li, Shuguang(1); Xu, Yantao(2); Zhang, Hao(2); Meng, Xiaojian(1); Guo, Ying(1); Wang, Chun(1); Wu, Biao(1); Zhao, Yuanyuan(1); Cui, Xingwang(1)
  Source: Guangxue Xuebao/Acta Optica Sinica  Volume: 43  Issue: 19  Article Number: 1906003  DOI: 10.3788/AOS230573  Published: 2023  
  Abstract:Objective As one of the important properties of the light field, polarization plays an important role in the interaction between light and matter. The modulation of polarization plays an indispensable role in optical communication systems, fiber sensors, fiber lasers, and other fields. However, in view of the twist, defects, environment perturbations, and other factors in the process of optical fiber manufacturing, the manufactured optical fiber is not completely uniform, which introduces random birefringence and leads to unpredictable polarization states. Therefore, it is of great practical value to study optical fibers with excellent polarization states. Although the existing single-polarization single-mode negative-curvature hollow-core fiber has the advantages of simple structure, easy preparation, endless single-mode transmission, and low loss, due to the limitation of research habits and optical materials, the current research mainly focuses on common communication bands. But obviously, the mid-infrared band will become the next hot band of the negative-curvature hollow-core fiber. Research shows that a wavelength of 3-5 µm plays an important role in national defense, medical care, communications, and other fields, especially near the wavelength of 4 µm, which is an ideal band for quantum cascade detectors to detect low-level light. Single-mode single-polarization light helps to provide a more pure light source for quantum cascade detectors. Therefore, it is of great practical significance to study the single-mode single-polarization negative-curvature hollow-core fiber with a wavelength of 4 µm. Methods A hollow-core anti-resonant fiber composed of six nested tubes working near 4 μm is designed, which can transmit single-mode single-polarization with low loss. The influence of structural parameters on fiber performance is calculated by using the control variable method. The capillary wall thickness will lead to an obvious change in the fiber loss with the working band, which is the key factor affecting the characteristics of the negative-curvature hollow-core antiresonant fiber. Therefore, the capillary wall thickness is analyzed and optimized. Through the scanning study of the capillary wall thickness, the local optimal parameter values of the minimum fundamental mode loss and the maximum high-order mode extinction ratio in the 4 μm band are determined, and the design goal of the single-mode performance of the fiber is successfully realized. The second step is to optimize the capillary radius. This parameter mainly affects the polarization state of the fiber, and different parameter combinations of the six inner tube radii correspond to different implementation effects. The optimization of capillary radius successfully achieves single-polarization operation in a single-mode state. In the third step, the core diameter of the fiber is optimized. Although the study does not reflect the further optimization effect of the parameters that have been optimized and determined in the previous steps, the parameter design still retains the effective mode area and the maximum transmission power tolerance value of the fiber. The fourth step is to study and characterize the bending resistance of optical fiber. Research shows that this design fully meets the preset requirements for bending resistance and verifies that the natural advantages of negative-curvature hollow-core anti-resonant fibers, such as large effective mode field area and less substrate material coverage, can contribute to the bending resistance of the fiber. Results and Discussions A negative-curvature hollow-core fiber with low-loss single-mode single-polarization transmission is proposed and analyzed by the finite element method. By calculating the influence of fiber parameters on the fiber structure, the high-order mode extinction ratio reaches 163 (Fig. 3), and the fiber successfully realizes single-mode transmission. However, in order to further ensure the single polarization performance of the fiber, the size of the capillary radius is optimized, and the single polarization function is realized based on single-mode transmission (Fig. 4). In order to ensure that the fiber has good bending resistance, the critical bending radius of the fiber is defined, and it is found that the bending loss of the x-polarization fundamental mode of the fiber is always less than 10−3 dB/m (Fig. 7). In addition, the fiber structure also has a large effective mode field area (Fig. 8), which meets the transmission requirements of high power lasers. The results show that the designed structure achieves both single-polarization performance and single-mode transmission. Conclusions In this paper, a single-mode, single-polarization, low-loss, negative-curvature, hollow-core, and antiresonant fiber is proposed. The substrate material of the fiber is As40S60, which is specially studied and experimentally prepared by Xi'an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences. Its refractive index is 2. 395 at 4 μm. It has low intrinsic loss and great chemical stability in the mid-infrared band, which is beneficial to realize the low loss performance of the fiber. The fiber structure adopts a six-nested, capillary-type, negative-curvature, hollow-core, and anti-resonant structure with relatively mature preparation technologies and a simple structure. After optimizing the parameters of the fiber, the single-mode single-polarization effect can be achieved from 3. 99 μm to 4. 00 μm. Especially at the wavelength of 4 μm, the polarization extinction ratio (PER) and high order mode extinction ratio (HOMER) reach 491 and 694, respectively, which meet the conditions of single-polarization single-mode transmission, and the loss is as low as 1. 8×10−4 dB/m. The fiber also has excellent bending resistance. At the wavelength of 4 μm, single-mode single-polarization transmission of the fiber can be achieved by selecting the appropriate bending radius at any bending angle. When the bending angle is equal to 0°, and the bending radius is from 1 cm to 10 cm, the confinement loss of the fiber is less than 5. 3×10−3 dB/m. The negative-curvature, hollow-core, and anti-resonant fiber proposed in this paper has the advantages of simple structure, single-mode single-polarization operation, low loss, and excellent bending resistance. It can not only be applied to the communication industry and medical system but also is expected to provide a more pure light source for quantum cascade detectors operating in the band of 4 μm. © 2023 Chinese Optical Society. All rights reserved.
  Accession Number: 20234815124764
• Record 461 of
  
  Title:Edge effect removal in Fourier ptychographic microscopy via periodic plus smooth image decomposition
  
  Author(s):Pan, An(1,2); Wang, Aiye(1,2,4); Zheng, Junfu(3); Gao, Yuting(1,2,4); Ma, Caiwen(1,2,4); Yao, Baoli(1,2)
  Source: Optics and Lasers in Engineering  Volume: 162  Issue: null  Article Number: 107408  DOI: 10.1016/j.optlaseng.2022.107408  Published: March 2023  
  Abstract:Fourier ptychographic microscopy (FPM) is a promising computational imaging technique with high resolution, wide field-of-view (FOV) and quantitative phase recovery. So far, a series of system errors that may corrupt the image quality of FPM has been reported. However, an imperceptible artifact caused by edge effect caught our attention and may also degrade the precision of phase imaging in FPM with a cross-shape artifact in the Fourier space. We found that the precision of reconstructed phase at the same subregion depends on the different sizes of block processing as a result of different edge conditions, which limits the quantitative phase measurements via FPM. And this artifact is caused by the aperiodic image extension of fast Fourier transform (FFT). Herein, to remove the edge effect and improve the accuracy, two classes of opposite algorithms termed discrete cosine transform (DCT) and periodic plus smooth image decomposition (PPSID) were reported respectively and discussed systematically. Although both approaches can remove the artifacts in FPM and may be extended to other Fourier analysis techniques, PPSID-FPM has a comparable efficiency to conventional FPM algorithm. The PPSID-FPM algorithm improves the standard deviation of phase accuracy as a factor of 4 from 0.08 radians to 0.02 radians. Finally, we summarized and discussed all the reported system errors of FPM within a generalized model. © 2022 Elsevier Ltd
  Accession Number: 20224813188122
• Record 462 of
  
  Title:Compact, repetition rate locked all-PM fiber femtosecond laser system based on low noise figure-9 Er:fiber laser
  
  Author(s):Cheng, Haihao(1,2); Zhang, Zhao(1,2); Pan, Ran(1,2); Zhang, Ting(1,2); Feng, Ye(1); Hu, Xiaohong(1); Wang, Yishan(1,2); Wu, Shun(1,3)
  Source: Optics and Laser Technology  Volume: 158  Issue: null  Article Number: 108818  DOI: 10.1016/j.optlastec.2022.108818  Published: February 2023  
  Abstract:We demonstrate a compact femtosecond fiber laser system based on all polarization-maintaining (PM) fiber and fiber components integrated structure. The figure-9 oscillator which incorporated a nonlinear amplifying loop mirror in the cavity features a 103.4-MHz high repetition rate with up to 93.1 dB signal-to-noise ratio of the radio frequency spectrum, 0.0056% [1 Hz, 1 MHz] integrated root-mean-square amplitude noise at the fundamental repetition rate and 63.7-fs timing jitter [100 Hz, 1 MHz]. Meanwhile, the fundamental repetition frequency was also locked to a stable radio frequency reference by using a self-designed frequency actuator and a relative frequency stability of 2.1 × 10−12 at 1-s gate time was obtained. Moreover, benefitting from the large positive group-velocity dispersion and negative third-order dispersion at 1.5-μm wavelength band, we also achieved 48.2 fs compressed pulse duration as well as an amplified average power of 199 mW via one-stage all-PM fiber amplifier and compressor. At last, as a performance proof, by directly splicing 38-cm long PM highly nonlinear fiber to the pulse compressor, a broadband coherent supercontinuum spanning from 950 nm to 2150 nm was generated. Our all-PM fiber laser system is suitable for the further buildup of a low noise PM fiber optical frequency comb. © 2022
  Accession Number: 20224413020441
• Record 463 of
  
  Title:COMD-free continuous-wave high-power laser diodes by using the multi-section waveguide method
  
  Author(s):Demir, Abdullah(1); Ebadi, Kaveh(1); Liu, Yuxian(2,3); Sünnetçioğlu, Ali Kaan(1); Gündoğdu, Sinan(1); Şengül, Serdar(1); Zhao, Yuliang(2,3); Lan, Yu(2,3); Yang, Guowen(2,3,4)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 12403  Issue: null  Article Number: 124030D  DOI: 10.1117/12.2650619  Published: 2023  
  Abstract:Catastrophic optical mirror damage (COMD) limits the output power and reliability of laser diodes (LDs). The self-heating of the laser contributes to the facet temperature, but it has not been addressed so far. This study investigates a two-section waveguide method targeting significantly reduced facet temperatures. The LD waveguide is divided into two electrically isolated sections along the cavity: laser and passive waveguide. The laser section is pumped at high current levels to achieve laser output. The passive waveguide is biased at low injection currents to obtain a transparent waveguide with negligible heat generation. This design limits the thermal impact of the laser section on the facet, and a transparent waveguide allows lossless transport of the laser to the output facet. Fabricated GaAs-based LDs have waveguide dimensions of (5-mm) x (100-µm) with passive waveguide section lengths varied from 250 to 1500 µm. The lasers were operated continuous-wave up to the maximum achievable power of around 15 W. We demonstrated that the two-section waveguide method effectively separates the heat load of the laser from the facet and results in much lower facet temperatures (Tf). For instance, at 8 A of laser current, the standard laser has Tf = 90 oC, and a two-section laser with a 1500 µm long passive waveguide section has Tf = 60 oC. While traditional LDs show COMD failures, the multi-section waveguide LDs are COMD-free. Our technique and results provide a pathway for high-reliability LDs, which would find diverse applications in semiconductor lasers. © 2023 SPIE.
  Accession Number: 20232114138209
• Record 464 of
  
  Title:Design of Underwater Wireless Optical Communication and Radar Integrated System
  
  Author(s):Li, Peng(1); Yang, Haodong(2); Wang, Shanglin(2); Tu, Min(2); Yan, Qiurong(2); Han, Xiaotian(1); Nie, Wenchao(1); Chang, Chang(1); Liao, Peixuan(1); Wang, Wei(1)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 12561  Issue: null  Article Number: 1256109  DOI: 10.1117/12.2651833  Published: 2023  
  Abstract:As a new type of technology, the integrated system of underwater wireless optical communication and radar will play a huge role in realizing flexible and high-speed communication links between underwater vehicles, underwater monitoring points, and marine vessels. It plays an important role in wireless sensor networks, ocean exploration and detection. This paper proposes an integrated system of underwater wireless optical communication and radar, which integrates the functions of communication and radar in the same system. A time-slot synchronous clock recovery method is proposed to recover communication signals and achieve high-reliability communication; a high-precision target imaging algorithm based on the first photon is proposed to achieve high-precision radar imaging. The communication performance is verified by simulation, and the influence of radar imaging quality is verified by experiment. The results show that the system can not only achieve the function of single-photon wireless optical communication, but also achieve the high-quality target imaging of single-photon level. © 2023 SPIE.
  Accession Number: 20230613560050
• Record 465 of
  
  Title:Hyperbolic resonant radiation of concomitant microcombs induced by cross-phase modulation
  
  Author(s):Wang, Yang(1,2); Wang, Weiqiang(1); Lu, Zhizhou(3); Wang, Xinyu(1,2); Huang, Long(1,2); Little, Brent E.(1); Chu, Sai T.(4); Zhao, Wei(1,2); Zhang, Wenfu(1,2)
  Source: Photonics Research  Volume: 11  Issue: 6  Article Number: null  DOI: 10.1364/PRJ.486977  Published: June 1, 2023  
  Abstract:A high-quality optical microcavity can enhance optical nonlinear effects by resonant recirculation, which provides a reliable platform for nonlinear optics research. When a soliton microcomb and a probe optical field are coexisting in a micro-resonator, a concomitant microcomb (CMC) induced by cross-phase modulation (XPM) will be formed synchronously. Here, we characterize the CMC comprehensively in a micro-resonator through theory, numerical simulation, and experimental verification. It is found that the CMCs spectra are modulated due to resonant radiation (RR) resulting from the interaction of dispersion and XPM effects. The group velocity dispersion induces symmetric RRs on the CMC, which leads to a symmetric spectral envelope and a dual-peak pulse in frequency and temporal domains, respectively, while the group velocity mismatch breaks the symmetry of RRs and leads to asymmetric spectral and temporal profiles. When the group velocity is linearly varying with frequency, two RR frequencies are hyperbolically distributed about the pump, and the probe light acts as one of the asymptotic lines. Our results enrich the CMC dynamics and guide microcomb design and applications such as spectral extension and dark pulse generation. © 2023 Chinese Laser Press.
  Accession Number: 20232814394340
• Record 466 of
  
  Title:48 W continuous-wave output power with high efficiency from a single emitter laser diode at 915 nm
  
  Author(s):Yang, Guowen(1,2,3); Liu, Yuxian(2,3); Zhao, Yongming(1); Tang, Song(1); Zhao, Yuliang(2,3); Lan, Yu(2,3); Bai, Longgang(1); Li, Ying(1); Wang, Ximin(1); Demir, Abdullah(4)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 12403  Issue: null  Article Number: 124030H  DOI: 10.1117/12.2650049  Published: 2023  
  Abstract:Improving the power and efficiency of 9xx-nm broad-area laser diodes reduces the cost of laser systems and expands applications. LDs with more than 25 W output power combined with power conversion efficiency (PCE) above 65% can provide a cost-effective high-power laser module. We report a high output power and high conversion efficiency laser diode operating at 915 nm by investigating the influence of the laser internal parameters on its output. The asymmetric epitaxial structure is optimized to achieve low optical loss while considering high internal efficiency, low series resistance, and modest optical confinement factor. Experimental results show an internal optical loss of 0.31 cm-1 and internal efficiency of 96%, in agreement with our simulation results. Laser diodes with 230 μm emitter width and 5 mm cavity length have T0 and T1 characteristic temperatures of 152 and 567 K, respectively. The maximum power conversion efficiency reaches 74.2% at 5 °C and 72.6% at 25 °C, and the maximum output power is 48.5 W at 48 A (at 30 ℃), the highest reported for a 9xx-nm single emitter laser diode. At 25 oC, a high PCE of 67.5% is achieved for the operating power of 30 W at 27.5 A, and the lateral far-field angle with 95% power content is around 8°. Life test results show no failure in 1200 hours for 55 laser diodes. In addition, 55.5 W output was achieved at 55 A from a laser diode with 400 μm emitter width and 5.5 mm cavity length. A high PCE of 64.3% is obtained at 50 W with 47 A. © 2023 SPIE.
  Accession Number: 20232114138213
• Record 467 of
  
  Title:Numerical simulation of the large-gap and small-gap pre-ionized direct-current glow discharges in atmospheric helium
  
  Author(s):Liu, Zaihao(1,2); Liu, Yinghua(1,2); Ran, Shuang(1,2); Xu, Boping(1,2); Yin, Peiqi(1,2); Li, Jing(3); Wang, Yishan(1,2); Zhao, Wei(1,2); Wang, Hui(4); Tang, Jie(1,2)
  Source: Physics of Plasmas  Volume: 30  Issue: 4  Article Number: 043507  DOI: 10.1063/5.0138129  Published: April 1, 2023  
  Abstract:A one-dimensional self-consistent fluid model was employed to comparatively investigate the influence of pre-ionization on the helium direct-current glow discharge in the large gap and the small gap at atmospheric pressure. For the large-gap and small-gap discharges, the negative glow space and the cathode fall layer are both offset to the cathode with the increase in pre-ionization, which is mainly ascribed to the decrease in charged particle density in the original negative glow space as a result of the increased probability of collision and recombination between ions and electrons, and the new balance between the positive and negative charges established at the distance closer to the cathode. The electron density tends to grow in the negative glow space due to the elevated pre-ionization, while the ion density exhibits an overall downward tendency in the cathode fall layer because the increase in secondary electrons produces more newly born electrons that neutralize more ions via the recombination reaction. Thanks to the pre-ionization, a significant reduction of sustaining voltage and discharge power is obtained in both the large-gap and small-gap discharges. A remarkable characteristic is that the absent positive column in the small-gap discharge comes into being again due to the pre-ionization. Moreover, with the increase in the pre-ionization level, the potential fall shifts from the cathode fall layer to the positive column in the large-gap discharge, while it is always concentrated in the cathode fall layer in the small-gap discharge. © 2023 Author(s).
  Accession Number: 20231713955230
• Record 468 of
  
  Title:Effect of La Doping on the Radiation Damage Effect of Er3+-Doped Silica Fibers for Space Laser Communication
  
  Author(s):Wen, Xuan(1); Yang, Shengsheng(1); Gao, Xin(1); She, Shengfei(2,3); Wang, Gencheng(2,3); Feng, Zhanzu(1); Wang, Jun(1); Yin, Hong(1); Hou, Chaoqi(2,3); Zhang, Jianfeng(1)
  Source: Guangzi Xuebao/Acta Photonica Sinica  Volume: 52  Issue: 2  Article Number: 0206003  DOI: 10.3788/gzxb20235202.0206003  Published: February 2023  
  Abstract:Space laser communication has the outstanding advantages of large transmission bandwidth，high transmission rate，and strong anti-interference ability，which is an important development direction of future communication technology. Since relay amplification cannot be realized in space laser communication links，a large transmission optical power is required in addition to ensuring a high modulation rate. Erbium-doped fiber amplifier achieves the amplification of 1.55 μm optical signal through the three-layer structure of erbium ions. The erbium-doped fiber is the core component of the erbium-doped fiber amplifier，and the erbium-doped fiber is a silicon fiber doped with a small number of erbium ions. In the space irradiation environment，high-energy particles impact the erbium-doped fiber，the core component of the erbium-doped fiber amplifier，resulting in a large number of carriers in the fiber，which combines with the original defects in the fiber to form new color-centered defects. The core defect leads to a dramatic increase in the loss of the fiber in the operating band，as well as a decrease in the gain performance of the erbium-doped fiber. As a rare earth element，La，like Er，is present in the interstitial positions of the quartz lattice structure. It can compete with Er ions for the interstitial positions and act as a dispersion of Er ions. It can achieve Al without affecting the maximum amount of Er ion doping. Low dose doping. La doping can disperse Er ions and suppress fluorescence quenching. There are few studies on the radiation effects of lanthanum-doped erbium-doped fibers. It is important to further understand the radiation-induced absorption mechanism of erbium-doped fibers to improve the performance of erbium-doped fibers in harsh environments. To verify the effect of La doping on the radiation resistance of erbium-doped fibers，two types of erbium-doped fibers，lanthanum-doped and non-lanthanum-doped，are selected in this paper，and the macroscopic radiation gain resistance performance and microstructural changes of the fibers are investigated. Radiation damage test study. The optical fiber was irradiated with a 60Co irradiation source at room temperature at a cumulative dose of 100 krad and a dose rate of 6.17 rad/s. The loss of the fiber was found to decrease along the wavelength direction in the range of 843~1 659 nm by electron probe tests and loss spectroscopy tests before and after irradiation，as well as online loss tests at specific wavelength points. However，the five fixed wavelength tests are not sufficient to fully express the loss variation of the fiber in each wavelength band under an irradiation environment. Offline loss tests were performed on both fibers before and after irradiation. The results showed that the increment before and after irradiation was 3 019 dB/km for S1 and 3 922 dB/km for S2. The loss increment of S2 after irradiation was significantly larger than that of S1 after irradiation. it was speculated that Al-OHC mainly caused the radiation-induced absorption. Absorption spectroscopy tests showed that La doping did not cause any change in the performance of Er ions in the fiber. the loss of the La-doped fiber at 1 200 nm was 0.030 67 dB/（km·krad），which was lower than 0.039 53 dB/（km·krad），and the gain of the La-doped fiber changed very little in the irradiated environment. The properties of the core matrix material did not change after irradiation by Raman testing，which proves that La doping does not cause changes in the glass lattice structure of the fiber. The paramagnetic defects of the fibers were further tested by electron paramagnetic resonance spectroscopy. The EPR signal intensities of the color-centered defects corresponding to Ge and Si did not differ much between the two types of light at 3 370 Gauss by fiber absorption spectroscopy and EPR tests. the peak at 3 330 Gauss is mainly due to the difference in Al content. the higher Al content in S2 produces a higher number of Al-OHC defects in the irradiated environment，and the corresponding EPR signal is stronger. the higher number of Al-OHC defects in S2 leads to a larger radiation-induced absorption in the 700~1 600 nm band，and the conclusion that the higher number of Al-OHC defects in S2 is consistent with the results of absorption spectroscopy tests before and after previous irradiation. The changes of Al-related paramagnetic defects in the fiber before and after irradiation were analyzed，indicating that the increase of Al content leads to more Al-OHC defects after irradiation，which in turn affects the gain performance of the fiber after irradiation. Further，by testing the gain performance of the two fibers before and after irradiation，it was found that the gain performance of the La-doped fiber changed less. It was verified that the loss and gain changes of the lanthanum- and erbium-doped fibers are smaller after irradiation，which indicates that lanthanum doping can improve the radiation resistance of the fibers. The doping of La can replace Al as the dispersant of Er ion to improve the radiation resistance of the fiber to a certain extent，and the doping of La does not negatively affect the gain performance of the fiber. This study can provide a reference for the radiation-hardening design of special optical fibers for subsequent space applications. © 2023 Chinese Optical Society. All rights reserved.
  Accession Number: 20231713945920