Letters|12 Article(s)
Fringe pattern analysis using deep learning|On the Cover
Shijie Feng, Qian Chen, Guohua Gu, Tianyang Tao, Liang Zhang, Yan Hu, Wei Yin, and Chao Zuo
In many optical metrology techniques, fringe pattern analysis is the central algorithm for recovering the underlying phase distribution from the recorded fringe patterns. Despite extensive research efforts for decades, how to extract the desired phase information, with the highest possible accuracy, from the minimum number of fringe patterns remains one of the most challenging open problems. Inspired by recent successes of deep learning techniques for computer vision and other applications, we demonstrate for the first time, to our knowledge, that the deep neural networks can be trained to perform fringe analysis, which substantially enhances the accuracy of phase demodulation from a single fringe pattern. The effectiveness of the proposed method is experimentally verified using carrier fringe patterns under the scenario of fringe projection profilometry. Experimental results demonstrate its superior performance, in terms of high accuracy and edge-preserving, over two representative single-frame techniques: Fourier transform profilometry and windowed Fourier transform profilometry.
Advanced Photonics
  • Publication Date: Feb. 28, 2019
  • Vol.1 Issue, 2 025001 (2019)
Robust and rapidly tunable light source for SRS/CARS microscopy with low-intensity noise|On the Cover
Heiko Linnenbank, Tobias Steinle, Florian Mörz, Moritz Flöss, Han Cui, Andrew Glidle, and Harald Giessen
Advanced Photonics
  • Publication Date: Sep. 24, 2019
  • Vol.1 Issue, 5 055001 (2019)
Mode-locked 2.8-μm fluoride fiber laser: from soliton to breathing pulse
Zhipeng Qin, Guoqiang Xie, Hongan Gu, Ting Hai, Peng Yuan, Jingui Ma, and Liejia Qian
The mode-locked fluoride fiber laser (MLFFL) is an exciting platform for directly generating ultrashort pulses in the mid-infrared (mid-IR). However, owing to difficulty in managing the dispersion in fluoride fiber lasers, MLFFLs are restricted to the soliton regime, hindering pulse-energy scaling. We overcame the problem of dispersion management by utilizing the huge normal dispersion generated near the absorption edge of an infrared-bandgap semiconductor and promoted MLFFL from soliton to breathing-pulse mode-locking. In the breathing-pulse regime, the accumulated nonlinear phase shift can be significantly reduced in the cavity, and the pulse-energy-limitation effect is mitigated. The breathing-pulse MLFFL directly produced a pulse energy of 9.3 nJ and pulse duration of 215 fs, with a record peak power of 43.3 kW at 2.8 μm. Our work paves the way for the pulse-energy and peak-power scaling of mid-IR fluoride fiber lasers, enabling a wide range of applications.
Advanced Photonics
  • Publication Date: Dec. 27, 2019
  • Vol.1 Issue, 6 065001 (2019)
Near-perfect microlenses based on graphene microbubbles
Han Lin, Scott Fraser, Minghui Hong, Manish Chhowalla, Dan Li, and Baohua Jia
Microbubbles acting as lenses are interesting for optical and photonic applications such as volumetric displays, optical resonators, integration of photonic components onto chips, high-resolution spectroscopy, lithography, and imaging. However, stable, rationally designed, and uniform microbubbles on substrates such as silicon chips are challenging because of the random nature of microbubble formation. We describe the fabrication of elastic microbubbles with a precise control of volume and curvature based on femtosecond laser irradiated graphene oxide. We demonstrate that the graphene microbubbles possess a near-perfect curvature that allows them to function as reflective microlenses for focusing broadband white light into an ultrahigh aspect ratio diffraction-limited photonic jet without chromatic aberration. Our results provide a pathway for integration of graphene microbubbles as lenses for nanophotonic components for miniaturized lab-on-a-chip devices along with applications in high-resolution spectroscopy and imaging.
Advanced Photonics
  • Publication Date: Oct. 07, 2020
  • Vol.2 Issue, 5 055001 (2020)
Preference of subpicosecond laser pulses for terahertz wave generation from liquids
Qi Jin, Yiwen E, Shenghan Gao, and Xi-Cheng Zhang
Advanced Photonics
  • Publication Date: Feb. 27, 2020
  • Vol.2 Issue, 1 015001 (2020)
Two-channel, dual-beam-mode, wavelength-tunable femtosecond optical parametric oscillator
Jintao Fan, Jun Zhao, Liping Shi, Na Xiao, and Minglie Hu
Optical vortices, which carry orbital angular momentum, offer special capabilities in a host of applications. A single-laser source with dual-beam-mode output may open up new research fields of nonlinear optics and quantum optics. We demonstrate a dual-channel scheme to generate femtosecond, dual-wavelength, and dual-beam-mode tunable signals in the near infrared wavelength range. Dual-wavelength operation is derived by stimulating two adjacent periods of a periodically poled lithium niobate crystal. Pumped by an Yb-doped fiber laser with a Gaussian (lp = 0) beam, two tunable signal emissions with different beam modes are observed simultaneously. Although one of the emissions can be tuned from 1520 to 1613 nm with the Gaussian (ls = 0) beam, the other is capable of producing a vortex spatial profile with different vortex orders (ls = 0 to 2) tunable from 1490 to 1549 nm. The proposed system provides unprecedented freedom and will be an exciting platform for super-resolution imaging, nonlinear optics, multidimensional quantum entanglement, etc.
Advanced Photonics
  • Publication Date: Jul. 06, 2020
  • Vol.2 Issue, 4 045001 (2020)
Far-field super-resolution imaging by nonlinearly excited evanescent waves
Zhihao Zhou, Wei Liu, Jiajing He, Lei Chen, Xin Luo, Dongyi Shen, Jianjun Cao, Yaping Dan, Xianfeng Chen, and Wenjie Wan
Advanced Photonics
  • Publication Date: Apr. 01, 2021
  • Vol.3 Issue, 2 025001 (2021)
High-dimensional orbital angular momentum multiplexing nonlinear holography
Xinyuan Fang, Haocheng Yang, Wenzhe Yao, Tianxin Wang, Yong Zhang, Min Gu, and Min Xiao
Nonlinear holography has been identified as a vital platform for optical multiplexing holography because of the appearance of new optical frequencies. However, due to nonlinear wave coupling in nonlinear optical processes, the nonlinear harmonic field is coupled with the input field, laying a fundamental barrier to independent control of the interacting fields for holography. We propose and experimentally demonstrate high-dimensional orbital angular momentum (OAM) multiplexing nonlinear holography to overcome this problem. By dividing the wavefront of the fundamental wave into different orthogonal OAM channels, multiple OAM and polarization-dependent holographic images in both the fundamental wave and second-harmonic wave have been reconstructed independently in the spatial frequency domain through a type-II second harmonic generation process. Moreover, this method can be easily extended to cascaded χ2 nonlinear optical processes for multiplexing in more wavelength channels, leading to potential applications in multicasting in optical communications, multiwavelength display, multidimensional optical storage, anticounterfeiting, and optical encryption.
Advanced Photonics
  • Publication Date: Jan. 01, 2021
  • Vol.3 Issue, 1 015001 (2021)
High spatial and temporal resolution synthetic aperture phase microscopy
Cheng Zheng, Di Jin, Yanping He, Hongtao Lin, Juejun Hu, Zahid Yaqoob, Peter T. C. So, and Renjie Zhou
A new optical microscopy technique, termed high spatial and temporal resolution synthetic aperture phase microscopy (HISTR-SAPM), is proposed to improve the lateral resolution of wide-field coherent imaging. Under plane wave illumination, the resolution is increased by twofold to around 260 nm, while achieving millisecond-level temporal resolution. In HISTR-SAPM, digital micromirror devices are used to actively change the sample illumination beam angle at high speed with high stability. An off-axis interferometer is used to measure the sample scattered complex fields, which are then processed to reconstruct high-resolution phase images. Using HISTR-SAPM, we are able to map the height profiles of subwavelength photonic structures and resolve the period structures that have 198 nm linewidth and 132 nm gap (i.e., a full pitch of 330 nm). As the reconstruction averages out laser speckle noise while maintaining high temporal resolution, HISTR-SAPM further enables imaging and quantification of nanoscale dynamics of live cells, such as red blood cell membrane fluctuations and subcellular structure dynamics within nucleated cells. We envision that HISTR-SAPM will broadly benefit research in material science and biology.
Advanced Photonics
  • Publication Date: Nov. 26, 2020
  • Vol.2 Issue, 6 065002 (2020)
Plasma-grating-induced breakdown spectroscopy
Mengyun Hu, Junsong Peng, Sheng Niu, and Heping Zeng
Laser-induced breakdown spectroscopy (LIBS) is a useful tool for determination of elements in solids, liquids, and gases. For nanosecond LIBS (ns-LIBS), the plasma shielding effect limits its reproducibility, repeatability, and signal-to-noise ratios. Although femtosecond laser filament induced breakdown spectroscopy (FIBS) has no plasma shielding effects, the power density clamping inside the filaments limits the measurement sensitivity. We propose and demonstrate plasma-grating-induced breakdown spectroscopy (GIBS). The technique relies on a plasma excitation source—a plasma grating generated by the interference of two noncollinear femtosecond filaments. We demonstrate that GIBS can overcome the limitations of standard techniques such as ns-LIBS and FIBS. Signal intensity enhancement with GIBS is observed to be greater than 3 times that of FIBS. The matrix effect is also significantly reduced with GIBS, by virtue of the high power and electron density of the plasma grating, demonstrating great potential for analyzing samples with complex matrix.
Advanced Photonics
  • Publication Date: Oct. 21, 2020
  • Vol.2 Issue, 6 065001 (2020)