2024

• Record 169 of
  
  Title:Secure FSO communication based on optical frequency-hopping technology using delay interferometers
  
  Author(s):Wang, Jian(1,2); Jin, Ya(1,2); Xie, Zhuang(3); Chen, Yinfang(1); Liu, Yu(1,2); Zhu, Ninghua(1,2)
  Source: Optics Communications  Volume: 550  Issue:   DOI: 10.1016/j.optcom.2023.129939  Published: January 1, 2024  
  Abstract:—A novel optical frequency-hopping (OFH) scheme using optical delay interferometers (DI) is proposed and demonstrated for secure transmission in free space. By performing carrier suppression modulation on the light wave emitted by the laser and connecting the phase modulator (PM) and DI in series, the conversion of the light wave modulated by the Mach-Zehnder modulator (MZM) from phase modulation to intensity modulation can be realized, and finally output the desired optical frequency-shift-keying (OFSK) carrier signal. Meanwhile, by controlling the positions of the frequencies of the positive and negative first-order sideband light waves on the DI frequency response curve, the OFSK signals output by the two ports of the DI can be complemented in the time domain. For the proposed OFH scheme, we carried out simulation experiments of 5 km free-space link transmission and back-to-back transmission with a communication rate of 10 Gbps, and the simulation results proved the feasibility of the scheme. Additionally, we also analyze the security performance of the proposed scheme and give the security space based on the eavesdropping probability. © 2023 Elsevier B.V.
  Accession Number: 20233914793103
• Record 170 of
  
  Title:Fast and Robust Restoration of Single Photon 3D Data Using Parameterized Kernel
  
  Author(s):Chen, Songmao(1,3); Su, Xiuqin(1,3); Zhang, Zhenyang(1,2,3); Xu, Weihao(1,2); Wang, Jie(1,2,3); Hao, Wei(1,3)
  Source: IEEE Journal of Selected Topics in Quantum Electronics  Volume: 30  Issue: 1  DOI: 10.1109/JSTQE.2023.3269747  Published: January 1, 2024  
  Abstract:Single photon 3D imaging is an emerging topic for optronic sensing under extreme scenarios (e.g. spaceborne altimeter, long range imaging). However, such technique suffers from low photon counts and strong noise, which is due to either strong attenuation from the environment or reduced acquisition time. Although state-of-the-art algorithms have been proposed to achieve high resolution results from corrupted single photon 3D data, the trade-off between the restoration performance and computational complexity remains challenging. This paper presents a fast and robust restoration approach for single photon 3D data, which adaptively smooth the sparse and noisy histogram by applying a parameterized kernel and finally reconstruct the 3D image using matched filter. The implementation can be fast as the core step of the processing is generalized as a 3D convolution that can be solved by Fast Fourier Transform (FFT). The method is validated on various conditions and scenarios from Middbury dataset and real data, where the proposed method showed robust results as the competing state-of-the-art algorithms with fast implementation. © 1995-2012 IEEE.
  Accession Number: 20232114129221
• Record 171 of
  
  Title:Alternating projection combined with fast gradient projection (FGP-AP) method for intensity-only measurement optical diffraction tomography in LED array microscopy
  
  Author(s):Yang, Zewen(1); Zhang, Lu(1,2); Liu, Tong(1); Wang, Huijun(1); Tang, Zhiyuan(3); Zhao, Hong(1,2); Yuan, Li(4); Zhang, Zhenxi(5); Liu, Xiaolong(6)
  Source: Biomedical Optics Express  Volume: 15  Issue: 4  DOI: 10.1364/BOE.518955  Published: April 1, 2024  
  Abstract:Optical diffraction tomography (ODT) is a powerful label-free measurement tool that can quantitatively image the three-dimensional (3D) refractive index (RI) distribution of samples. However, the inherent "missing cone problem,"limited illumination angles, and dependence on intensity-only measurements in a simplified imaging setup can all lead to insufficient information mapping in the Fourier domain, affecting 3D reconstruction results. In this paper, we propose the alternating projection combined with the fast gradient projection (FGP-AP) method to compensate for the above problem, which effectively reconstructs the 3D RI distribution of samples using intensity-only images captured from LED array microscopy. The FGP-AP method employs the alternating projection (AP) algorithm for gradient descent and the fast gradient projection (FGP) algorithm for regularization constraints. This approach is equivalent to incorporating prior knowledge of sample non-negativity and smoothness into the 3D reconstruction process. Simulations demonstrate that the FGP-AP method improves reconstruction quality compared to the original AP method, particularly in the presence of noise. Experimental results, obtained from mouse kidney cells and label-free blood cells, further affirm the superior 3D imaging efficacy of the FGP-AP method. © 2024 Optica Publishing Group.
  Accession Number: 20241815995654
• Record 172 of
  
  Title:Simulation Analysis of Key Parameters for CH4 Gas Point Source Detection Based on F-P Interferometer
  
  Author(s):Zhang, Qiang(1,2); Bai, Caixun(3); Fu, Di(1); Li, Juan(2); Chang, Chenguang(1); Zhao, Hengxiang(1); Wang, Sufeng(1); Feng, Yutao(1)
  Source: Guangzi Xuebao/Acta Photonica Sinica  Volume: 53  Issue: 1  DOI: 10.3788/gzxb20245301.0130001  Published: January 2024  
  Abstract:The increase in greenhouse gases carbon dioxide and methane can directly lead to changes in the global climate and cause a significant impact on the economies of countries and human life. Methane，as the second-largest greenhouse gas on Earth，has a global warming potential 30 times higher than CO2 over a 100-year period，and its lifespan is approximately 9.1 years. At present，anthropogenic CH4 emissions primarily originate from numerous point sources. Implementing measures to reduce CH4 emissions can help decrease the rate of global warming. Therefore，it is crucial to conduct research on monitoring technologies for CH4 and investigate key carbon emission sources. Hyperspectral satellite remote sensing for detecting greenhouse gases has become a candidate technology for point source detection. It has advantages such as high viewpoint，wide field of view，the ability to achieve dynamic monitoring，obtain more precise and demand-driven information data. Utilizing remote sensing methods to monitor and provide feedback on point source emissions of greenhouse gases like methane plays a crucial role in effectively addressing climate change. Existing payload technologies in China are geared towards large satellite platforms，enabling wide-area coverage with low spatial resolution monitoring. However，traditional methods such as grating spectrometry，Michelson interferometry，and spatial heterodyne are unable to meet the efficient and high-precision monitoring requirements for small-scale anthropogenic emission sources. They struggle to achieve point source detection. Therefore，it is necessary to conduct research on satellite remote sensing carbon monitoring technologies that offer high accuracy and high spatial resolution. The Fabry-Pérot interferometry technique possesses extremely high spectral resolution，capable of discerning minute wavelength differences in the spectrum. The theoretical basis of this technique is the multi-beam equal-inclination interferometry. By using an interference ring，it is possible to directly obtain the spectral information of target light at different incident angles. By collecting the spectral information corresponding to different wavelengths of the target at different positions from multiple consecutive shots，the target spectral curve is obtained. This technique establishes a relationship between CH4 gas concentration and the depth of spectral curve notches，offering advantages in point source detection with high spectral resolution and high spatial resolution. In CH4 gas detection，the parameters of the Fabry-Pérot interferometer and the optical filter have a significant impact on detection sensitivity. Properly configuring these parameters is crucial for improving detection accuracy. This paper presents a study on a high spatial resolution method for detecting point sources of methane gas based on the principle of multi-beam interferometric spectral imaging. Firstly，the working principle and detection scheme of the methane gas detector are introduced. The system parameters of the Fabry-Pérot interferometer are designed， and a forward model for methane gas detection is established. Subsequently，the correspondence between interference signals and methane concentration，as well as the influence of instrument parameters on detection sensitivity，are analyzed. In the end，iterative optimization is performed to obtain the optimal values of various optical structural parameters. The results indicate that within the methane detection wavelength range of 1 630~1 675 nm，with a free spectral range of 12.5 nm and a spectral resolution of 0.1 nm，the optimal parameters for the Fabry-Pérot interferometer are a cavity length of 0.08 mm and an intra-cavity reflectance of 97.5%. By using a cutoff filter with a range of（1 630±4）nm ~ （1 675±4）nm，the relative change in interference signal corresponding to a 25% concentration variation of the detection source falls within the range of［0.65%，4.30%］，indicating a good detection sensitivity. The research results of this study provide a theoretical basis and technical support for high-precision. © 2024 Chinese Optical Society. All rights reserved.
  Accession Number: 20240815582116
• Record 173 of
  
  Title:Domain Adaptation of Anchor-Free object detection for urban traffic
  
  Author(s):Yu, Xiaoyong(1,2); Lu, Xiaoqiang(3)
  Source: Neurocomputing  Volume: 582  Issue:   DOI: 10.1016/j.neucom.2024.127477  Published: May 14, 2024  
  Abstract:Modern detectors are mostly trained under single and limited conditions. However, object detection faces various complex and open situations in autonomous driving, especially in urban street scenes with dense objects and complex backgrounds. Due to the shift in data distribution, modern detectors cannot perform well in actual urban environments. Using domain adaptation to improve detection performance is one of the key methods to extend object detection from limited situations to open situations. To this end, this article proposes a Domain Adaptation of Anchor-Free object detection (DAAF) for urban traffic. DAAF is a cross-domain object detection method that performs feature alignment including two aspects. On the one hand, we designed a fully convolutional adversarial training method for global feature alignment at the image level. Meanwhile, images can generally be decomposed into structural information and texture information. In urban street scenes, the structural information of images is generally similar. The main difference between the source domain and the target domain is texture information. Therefore, during global feature alignment, this paper proposes a method called texture information limitation (TIL). On the other hand, in order to solve the problem of variable aspect ratios of objects in urban street scenes, this article uses an anchor-free detector as the baseline detector. Since the anchor-free object detector can obtain neither explicit nor implicit instance-level features, we adopt Pixel-Level Adaptation (PLA) to align local features instead of instance-level alignment for local features. The size of the object has the greatest impact on the final detection effect, and the object scale in urban scenes is relatively rich. Guided by the differentiation of attention mechanisms, a multi-level adversarial network is designed to perform feature alignment of the output space at different feature levels called Scale Information Limitation (SIL). We conducted cross-domain detection experiments by using various urban streetscape autonomous driving object detection datasets, including adverse weather conditions, synthetic data to real data, and cross-camera adaptation. The experimental results indicate that the method proposed in this article is effective. © 2024 Elsevier B.V.
  Accession Number: 20241215767931
• Record 174 of
  
  Title:Flexible fiberbotic laser scalpels: Material and fabrication challenges
  
  Author(s):Zou, Yuqi(1,2); Ren, Zhihe(1,2); Xiang, Yuanzhuo(1,2); Liu, Chao(1,2); Gao, Anzhu(3,4); Huang, Shaoping(4); Yang, Lvyun(1); Hou, Chong(5); Guo, Haitao(6); Yang, Guang-Zhong(4); Tao, Guangming(1,2,4)
  Source: Matter  Volume: 7  Issue: 3  DOI: 10.1016/j.matt.2024.01.007  Published: March 6, 2024  
  Abstract:Rapidly developed fiber lasers have shown great potential in interventional urology, inspiring the use of advanced laser delivery to meet the demand for manipulation in other complex surgical scenarios. While medical robots are enhancing precision in the field of minimally invasive surgery, laser ablation has been demonstrated as a promising candidate compared to traditional mechanical cutting tools in interventions. Nevertheless, based on their ablation mechanisms, the advantages of lasers are still not fully leveraged. In this Perspective, we outline how fiber-shaped robots combined with laser scalpels are primed to emerge as the next generation of medical robots to achieve minimally invasive surgery. We review the mechanisms involved, analyze their applications, and discuss several prospects for future applications. © 2024 Elsevier Inc.
  Accession Number: 20240915657499
• Record 175 of
  
  Title:Optimal design of a gravitational wave telescope system for the suppression of stray light
  
  Author(s):Liang, Rong(1,2); Zhou, Xiaojun(1); Xu, Huangrong(1); Wu, Dengshan(1); Li, Chenxi(1); Yu, Weixing(1,2)
  Source: Applied Optics  Volume: 63  Issue: 8  DOI: 10.1364/AO.502610  Published: March 10, 2024  
  Abstract:For gravitational wave detection, the telescope is required to have an ultra-low wavefront error and ultra-high signal-to-noise ratio, where the power of the stray light should be controlled on the order of less than 10-10. In this work, we propose an alternative stray light suppression method for the optical design of an off-axis telescope with four mirrors by carefully considering the optimal optical paths. The method includes three steps. First, in the period of the optical design, the stray light caused by the tertiary mirror and the quaternary mirror is suppressed by increasing the angle formed by the optical axes of the tertiary mirror and the quaternary mirror and reducing the radius of curvature of the quaternary mirror as much as possible to make sure the optical system provides a beam quality with a wavefront error less than λ/80. Next, the stray light could satisfy the requirement of the order of 10-10 when the level of roughness reaches 0.2 nm, and the pollution of mirrors is controlled at the level of CL100. Finally, traditional stray light suppression methods should also be applied to mechanics, including the use of the optical barrier, baffle tube, and black paint. It can be seen that the field stop can efficiently reduce stray light caused by the secondary mirror by more than 55% in the full field of view. The baffle tube mounted on the position of the exit pupil can reduce the overall stray light energy by 5%, and the difference between the ideal absorber (absorption coefficient is 100%) and the actual black paint (absorption coefficient is 90%) is 3.2%. These simulation results are confirmed by theMonte Carlo method for a stray light analysis. Based on the above results, one can conclude that the geometry structure of the optical design, the quality of mirrors, and the light barrier can greatly improve the stray light suppression ability of the optical system, which is vital when developing a gravitational wave telescope with ultra-lowstray light energy. © 2024 Optica Publishing Group.
  Accession Number: 20241215786774
• Record 176 of
  
  Title:Laser-guided anisotropic etching for precision machining of micro-engineered glass components
  
  Author(s):Li, Jun(1); Zhong, Shuai(1); Huang, Jiaxu(1); Qiu, Pei(1); Wang, Pu(1,2); Li, Hui(1); Qin, Chu(3); Miao, Duo(1); Xu, Shaolin(1)
  Source: International Journal of Machine Tools and Manufacture  Volume: 198  Issue:   DOI: 10.1016/j.ijmachtools.2024.104152  Published: May 2024  
  Abstract:Micro-engineered glass components play a vital role in various domains, but their full potential remains untapped due to the lack of easily accessible high-precision machining methods for customizable microstructure. Our discovery of a new phenomenon, where laser-modified regions break the rule of inherently isotropic glass etching and regulate a directional anisotropic etching along modified tracks, has led to the development of a laser-guided anisotropic etching (LGAE) method. This method enables crafting precision glass microstructures with sharp features, smooth surfaces, and adjustable shapes and sizes. An ultrafast Bessel beam is utilized to create high aspect-ratio line-shaped modification within the glass. With a higher etching rate than pristine glass, the modified line guides directional anisotropic etching along the modified track, facilitating the formation of a V-shape with an angle altered by the etching ratio. These modified lines can further serve as basic building blocks to interconnect to construct a 3D internal modification region and then guide the glass's overall surface morphology etching evolution, enabling the creation of microstructures featuring designable shapes and adjustable feature sizes. To accurately predict and control the shape of the microstructures, we establish a finite difference etching model that incorporates localized etching rate regulation, validating the robustness and controllability of LGAE. This scalable method has successfully fabricated a 50 μm period micro-pyramid array with high uniformity over a centimeter-scale area, demonstrating its suitability for large-scale manufacturing. The showcased micro-engineered glass components encompass V-groove arrays for fiber alignment, blazed gratings for light modulation, and microchannels with customized trajectories for microfluidic chips. These advancements driven by LGAE can significantly contribute to the progress of glass-based research and industries. © 2024 Elsevier Ltd
  Accession Number: 20241515905919
• Record 177 of
  
  Title:Analysis and simulation of the effect of large optical range difference of common path coherent-dispersion spectrometer on the detection of exoplanet radial velocities
  
  Author(s):Guan, Shouxin(1,2); Liu, Bin(1,2); Chen, Shasha(1); Wu, Yinhua(3); Wang, Feicheng(1,2); Wang, Shaofei(6); Liu, Xuebin(1); Wei, Ruyi(4,5,6)
  Source: Optics Communications  Volume: 561  Issue:   DOI: 10.1016/j.optcom.2024.130443  Published: June 15, 2024  
  Abstract:The Exoplanet Explorer common-path coherent-dispersion spectrometer (CODES) utilizes a unique combination of an asymmetric common path Sagnac interferometer and a low to medium resolution spectrometer. The ideal optical range difference (OPD) interval for CODES is OPD ∈ {15.06 mm, 19.45 mm}; however, the OPD of CODES is 64.3 mm to achieve better detection accuracy. Though they will increase the accuracy of detection, large OPDs outside of the ideal interval will also reduce the contrast of the interference fringes, making phase changes more hazy. This may also significantly affect the radial velocity inversion and reduce CODES's instrumental accuracy. This study creates an inverse tone mapping operator based on the photographic model and designs an inverse tone mapping algorithm called CODESCE. The outcomes of the experiments demonstrate that the tone mapping algorithm CODESCE in this work is appropriate for enhancing the contrast of interference fringe images with high OPD, and it can enhance the contrast of interference fringes by three orders of magnitude when OPD = 64.3 mm; the processed interference fringes are located in the range of interference fringe curves of the optimal OPD. By comparison with other current approaches, the suggested algorithm yields superior processing outcomes. © 2024
  Accession Number: 20241415840369
• Record 178 of
  
  Title:Performance improvement of a discrete dynode electron multiplication system through the optimization of secondary electron emitter and the adoption of double-grid dynode structure
  
  Author(s):Liu, Biye(1,2); Li, Jie(1); Chen, Song(3); Yang, Jishi(1); Hu, Wenbo(1); Tian, Jinshou(4); Wu, Shengli(1)
  Source: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment  Volume: 1062  Issue:   DOI: 10.1016/j.nima.2024.169162  Published: May 2024  
  Abstract:The discrete dynode electron multiplication system (DD-EMS) is the core part of commonly used photomultiplier tubes and electron multipliers, and it has a great influence on the signal amplification capability of these devices. In this work, the sputtering time of Mg target during the deposition of the surface MgO layer of the MgO/(MgO–Au)/Au multilayer film as the secondary electron emitter was optimized, and the strategy of double-grid structures applied at the 7th and 8th dynodes was proposed with the intention of improving the gain and stability of nine-stage DD-EMS under electron bombardment to satisfy the requirements of detecting the single photon or single charged particle. The investigation results show that the DD-EMS fabricated by using the MgO/(MgO–Au)/Au film with a Mg target's sputtering time of 3600 s has the highest maximal gain of 1.22 × 106 and the lowest gain attenuation rate of 15.7%/mC under electron bombardment. In addition, the DD-EMS with the double-grid structure has a higher maximal gain of 1.62 × 106 and a lower gain attenuation rate of 11.6%/mC under continuous electron bombardment, which are 32.8% increased and 17.7% reduced respectively in comparison with that of the single-grid structure. © 2024 Elsevier B.V.
  Accession Number: 20240815578823
• Record 179 of
  
  Title:Design and fabrication of a tellurite hollow-core anti-resonant fiber for mid-infrared applications
  
  Author(s):Zhu, Jun(1,2); Feng, Shaohua(1,2); Liu, Chengzhen(1,2); Cai, Liyang(1,2); Xu, Yantao(1,2); Xiao, Xusheng(1,2); Guo, Haitao(1,2,3)
  Source: Optics Express  Volume: 32  Issue: 8  DOI: 10.1364/OE.519034  Published: April 8, 2024  
  Abstract:The hollow core anti-resonant fibers (HC-ARFs) based on soft glass are in high demand for 3-6 µm laser delivery. A HC-ARF based on tellurite glass with 6 touching capillaries as cladding was designed and fabricated for the first time, to the best of our knowledge. A relatively low loss of 3.75 dB/m at 4.45 µm was realized in it. The effects of capillary number, core diameter, wall thickness of capillary, and material absorption loss on the loss of the HC-ARF were analyzed by the numerically simulation. The output beam quality was measured and the influence of bending on the fiber loss was discussed. The results of numerical simulation suggested that the theoretical loss of the prepared fiber can be reduced to 0.1 dB/m, indicating that tellurite HC-ARFs have great potential for mid-infrared laser applications. © 2024 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement.
  Accession Number: 20241615913638
• Record 180 of
  
  Title:Multi-Aperture Joint-Encoding Fourier Ptychography for a Distributed System
  
  Author(s):Wang, Tianyu(1,2); Xiang, Meng(1,2,3); Liu, Fei(2); Liu, Jinpeng(1,2,3); Dong, Xue(1,2,4); Wang, Sen(1,2); Li, Gang(5); Shao, Xiaopeng(1,2)
  Source: Remote Sensing  Volume: 16  Issue: 6  DOI: 10.3390/rs16061017  Published: March 2024  
  Abstract:High-resolution infrared remote sensing imaging is critical in planetary exploration, especially under demanding engineering conditions. However, due to diffraction, the spatial resolution of conventional methods is relatively low, and the spatial bandwidth product limits imaging systems’ design. Extensive research has been conducted with the aim of enhancing spatial resolution in remote sensing using a multi-aperture structure, but obtaining high-precision co-phase results using a sub-aperture remains challenging. A new high-resolution imaging method utilizing multi-aperture joint-encoding Fourier ptychography (JEFP) is proposed as a practical means to achieve super-resolution infrared imaging using distributed platforms. We demonstrated that the JEFP approach achieves pixel super-resolution with high efficiency, without requiring subsystems to perform mechanical scanning in space or to have high position accuracy. Our JEFP approach extends the application scope of Fourier ptychographic imaging, especially in distributed platforms for planetary exploration applications. © 2024 by the authors.
  Accession Number: 20241515862188