Contents
2021
Volume: 19 Issue 5
18 Article(s)

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Research Articles
Biophotonics
Deep-learning-based prediction of living cells mitosis via quantitative phase microscopy
Ying Li, Jianglei Di, Li Ren, and Jianlin Zhao
We present a deep learning approach for living cells mitosis classification based on label-free quantitative phase imaging with transport of intensity equation methods. In the approach, we applied a pretrained deep convolutional neural network using transfer learning for binary classification of mitosis and non-mitosis. As a validation, we demonstrated the performances of the network trained by phase images and intensity images, respectively. The convolutional neural network trained by phase images achieved an average accuracy of 98.9% on the validation data, which outperforms the average accuracy 89.6% obtained by the network trained by intensity images. We believe that the quantitative phase microscopy in combination with deep learning enables researchers to predict the mitotic status of living cells noninvasively and efficiently.
Chinese Optics Letters
  • Publication Date: Mar. 18, 2021
  • Vol.19 Issue, 5 051701 (2021)
Diffraction, Gratings, and Holography
Pattern-adaptive error diffusion algorithm for improved phase-only hologram generation
Kexuan Liu, Zehao He, and Liangcai Cao
The bidirectional error diffusion (BERD) algorithm is free from random phase modulation that introduces speckle noise on the reconstructed images, compared with other computer-generated phase-only hologram (POH) approaches. During the POH generation process, the amplitudes of all pixels are traditionally set to one for diffusing the errors to their neighborhood of unprocessed pixels. In this paper, we reveal that the reconstruction quality depends on the uniform amplitude value for different object pattern. The pattern-adaptive BERD (PA-BERD) algorithm is proposed for high-quality holographic reconstruction. The optimized amplitude value can be acquired for each object pattern and each propagation distance. The PA-BERD-based POHs have shown higher reconstruction quality than traditional BERD-based POHs in simulations as well as optical experiments.
Chinese Optics Letters
  • Publication Date: Feb. 25, 2021
  • Vol.19 Issue, 5 050501 (2021)
Fiber Optics and Optical Communications
Multi-focus optical fiber lens based on all-dielectric metasurface
Xingyu Zhang, Chunying Guan, Keda Wang, Lin Cheng, Jing Yang, Jinhui Shi, Hongchao Liu, Zhihai Liu, and Libo Yuan
A multi-focus optical fiber lens is numerically demonstrated based on an all-dielectric metasurface structure. The metasurface consists of an array of rectangular silicon resonators with varying widths in order to obtain the required phase distribution. The core diameter of the multimode fiber is large enough to contain sufficient resonance units. The spatial distribution of the dielectric resonators is dictated by spatial multiplexing, including interleaving meta-atoms and lens aperture division, to achieve multi-focus properties. The proposed optical fiber metalens can produce two or three focal points along the longitudinal direction with high focusing efficiency. The size of every focal point is close to the diffraction limit, and the relative intensity on each focus can be controlled by adjusting the number of the respective resonators. The proposed optical fiber lens will have a great potential in the fields of integrated optics and multifunctional micro/nano devices.
Chinese Optics Letters
  • Publication Date: Feb. 25, 2021
  • Vol.19 Issue, 5 050601 (2021)
Secure orthogonal time-frequency multiplexing with two-dimensional encryption for optical-wireless communications
Jie Zhong, Ji Zhou, Shecheng Gao, and Weiping Liu
This paper firstly, to the best of our knowledge, proposed two-dimensional (2D) encryption based on the Arnold transformation for implementing a secure DC-biased optical orthogonal time-frequency multiplexing (DCO-OTFM) in optical-wireless communications (OWCs). The encrypted data is transformed to the particular 2D matrix and decrypted by the only key to get the correct information. Meanwhile, the number of keys in 2D encryption is enormous, which prevents eavesdroppers from exhaustively searching secret keys rapidly to find the right decryption. Numerical results demonstrate that the secure DCO-OTFM based on 2D encryption can effectively prevent signal decryption from the eavesdropper, which has good secure performance for applying in OWC.
Chinese Optics Letters
  • Publication Date: Feb. 25, 2021
  • Vol.19 Issue, 5 050603 (2021)
Machine-vision-based acquisition, pointing, and tracking system for underwater wireless optical communications
Jiaming Lin, Zihao Du, Chuying Yu, Wenmin Ge, Weichao Lü, Huan Deng, Chao Zhang, Xiao Chen, Zejun Zhang, and Jing Xu
Due to the proliferation of underwater vehicles and sensors, underwater wireless optical communication (UWOC) is a key enabler for ocean exploration with a strong reliance on short-range bandwidth-intensive communications. A stable optical link is of primary importance for UWOC. A compact, low-power, and low-cost acquisition, pointing, and tracking (APT) system is proposed and experimentally demonstrated to realign the optical link within 0.04 s, even when the UWOC transmitter and receiver are in relative motion. The system successfully achieves rapid auto-alignment through a 4 m tap water channel with a relatively large number of bubbles. Furthermore, the required minimum illumination value is measured to be as low as 7.1 lx, implying that the proposed APT scheme is robust to dim underwater environments. Meanwhile, mobility experiments are performed to verify the performance of the APT system. The proposed system can rapidly and automatically align moving targets in complex and unstable underwater environments, which can potentially boost the practical applications of UWOC.
Chinese Optics Letters
  • Publication Date: Mar. 03, 2021
  • Vol.19 Issue, 5 050604 (2021)
Instrumentation, Measurement, and Optical Sensing
Design of low frequency fiber optic Fabry–Perot seismometer based on transfer function analysis
Huicong Li, Wentao Zhang, Wenzhu Huang, and Yanliang Du
Chinese Optics Letters
  • Publication Date: Mar. 18, 2021
  • Vol.19 Issue, 5 051201 (2021)
Integrated Optics
Thermally tunable microfiber knot resonator with flexible graphene heater
Yunzheng Wang, Qing Wu, Huide Wang, Jiefeng Liu, Zheng Zheng, Meng Zhang, and Han Zhang
Chinese Optics Letters
  • Publication Date: Mar. 03, 2021
  • Vol.19 Issue, 5 051301 (2021)
Lasers, Optical Amplifiers, and Laser Optics
Effective strategy to achieve a metal surface with ultralow reflectivity by femtosecond laser fabrication
Xun Li, Ming Li, and Hongjun Liu
Chinese Optics Letters
  • Publication Date: Feb. 25, 2021
  • Vol.19 Issue, 5 051401 (2021)
Nanophotonics, Metamaterials, and Plasmonics
Independent phase manipulation of co- and cross-polarizations with all-dielectric metasurface
Haoyu Wang, Zhiyu Zhang, Kun Zhao, Wen Liu, Pei Wang, and Yonghua Lu
Phase carried by two orthogonal polarizations can be manipulated independently by controlling both the geometric size and orientation of the dielectric nanopost. With this characteristic, we demonstrate a novel multifunctional metasurface, which converts part of the incident linearly polarized light into its cross-polarization and encodes the phase of the two orthogonal polarizations independently. A beam splitter and a bifocal metalens were realized in a single-layer dielectric metasurface by this approach. We fabricated the bifocal metalens and demonstrated that two focal spots in orthogonal polarizations can be separated transversely or longitudinally at will. The proposed approach shows a new route to design multifunctional metasurfaces with various applications in holography and three-dimensional display.
Chinese Optics Letters
  • Publication Date: Mar. 03, 2021
  • Vol.19 Issue, 5 053601 (2021)
Laser printing based on curvature-driven shape transition of aluminum nanodiscs [Invited] | Editors' Pick
Yudong Lu, Dejiao Hu, Mingsi Zhang, Lechen Yang, Jiafang Li, Yaoyu Cao, and Xiangping Li
Plasmonic structural colors have plenty of advantages over traditional colors based on colorants. The pulsed laser provides an important method generating plasmonic structural colors with high efficiency and low cost. Here, we present plasmonic color printing Al nanodisc structures through curvature-driven shape transition. We systematically study the mechanism of morphologic evolution of the Al nanodisc below the thermal melting threshold. A multi-pulse-induced accumulated photothermal effect and subsequent curvature-driven surface atom diffusion model are adopted to explain the controllable shape transition. The shape transition and corresponding plasmonic resonances of the nanodisc can be independently and precisely modulated by controlled irradiations. This method opens new ways towards high-fidelity color prints in a highly efficient and facile laser writing fashion.
Chinese Optics Letters
  • Publication Date: Feb. 04, 2021
  • Vol.19 Issue, 5 053602 (2021)
Nonlinear Optics
Double-slit diffraction of terahertz wave generated by tilted-pulse-front pumping
Shangqing Li, Jinglong Ma, Xiaojun Wu, Baolong Zhang, Chen Ouyang, Tianze Wang, Dan Wang, Xuan Wang, and Yutong Li
Chinese Optics Letters
  • Publication Date: Feb. 25, 2021
  • Vol.19 Issue, 5 051901 (2021)
Optical Materials
Physical Optics
Optimizing illumination’s complex coherence state for overcoming Rayleigh’s resolution limit
Chunhao Liang, Yashar E. Monfared, Xin Liu, Baoxin Qi, Fei Wang, Olga Korotkova, and Yangjian Cai
Chinese Optics Letters
  • Publication Date: Feb. 25, 2021
  • Vol.19 Issue, 5 052601 (2021)
Quantum Optics and Quantum Information
Engineering the spectral profile of photon pairs by using multi-stage nonlinear interferometers
Mingyi Ma, Liang Cui, and Xiaoying Li
Using the quantum interference of photon pairs in N-stage nonlinear interferometers (NLIs), the contour of the joint spectral function can be modified into an islands pattern. We perform two series of experiments. One is that all of the nonlinear fibers in pulse pumped NLIs are identical; the other is that the lengths of N pieces of nonlinear fibers are different. We not only demonstrate how the pattern of spectral function changes with the stage number N, but also characterize how the relative intensity of island peaks varies with N. The results well agree with theoretical predictions, revealing that the NLI with lengths of N pieces of nonlinear fibers following binomial distribution can provide a better active filtering function. Our investigation shows that the active filtering effect of multi-stage NLI is a useful tool for efficiently engineering the factorable two-photon state—a desirable resource for quantum information processing.
Chinese Optics Letters
  • Publication Date: Mar. 18, 2021
  • Vol.19 Issue, 5 052702 (2021)
Noise transfer of pump field noise with analysis frequency in a broadband parametric downconversion process
Yajun Wang, Yuhang Tian, Xiaocong Sun, Long Tian, and Yaohui Zheng
Chinese Optics Letters
  • Publication Date: Mar. 03, 2021
  • Vol.19 Issue, 5 052703 (2021)
Reviews
Physical Optics
Topological photonic states in artificial microstructures [Invited] | On the Cover
Hui Liu, Boyang Xie, Hua Cheng, Jianguo Tian, and Shuqi Chen
Topological photonics provides a new opportunity for the examination of novel topological properties of matter, in which the energy band theory and ideas in topology are utilized to manipulate the propagation of photons. Since the discovery of topological insulators in condensed matter, researchers have studied similar topological effects in photonics. Topological photonics can lead to materials that support the robust unidirectional propagation of light without back reflections. This ideal transport property is unprecedented in traditional optics and may lead to radical changes in integrated optical devices. In this review, we present the exciting developments of topological photonics and focus on several prominent milestones of topological phases in photonics, such as topological insulators, topological semimetals, and higher-order topological phases. We conclude with the prospect of novel topological effects and their applications in topological photonics.
Chinese Optics Letters
  • Publication Date: Feb. 04, 2021
  • Vol.19 Issue, 5 052602 (2021)