Amplitude-phase optimized long depth of focus femtosecond axilens beam for single-exposure fabrication of high-aspect-ratio microstructures

Author(s):

Deng Pan, Bing Xu, Shunli Liu, Jiawen Li, Yanlei Hu, Dong Wu, and Jiaru Chu

Abstract:

“Fabrication of high-aspect-ratio (HAR) micro/nanostructures by two-photon polymerization (TPP) has become a hot topic because of the advantages of ultra-high resolution and true 3D printing ability. However, the low efficiency caused by point-by-point scanning strategy limits its application. In this Letter, we propose a strategy for the rapid fabrication of HAR microstructures by combining TPP with an amplitude-phase optimized long depth of focus laser beam (LDFB). The optimization of the LDFB is implemented by modulating the amplitude and phase on a phase-only spatial light modulator, which can suppress the side lobe and smooth energy oscillations effectively. The LDFB is used for rapid fabrication of HAR micropillars and various microstructures, which greatly increases the fabrication efficiency. As a demonstration, several typical HAR microstructures such as assemblies, microchannels, microtubes, and cell scaffolds are prepared. Moreover, the microcapture arrays are rapidly fabricated for the capture of microspheres and the formation of microlens arrays, which show focusing and imaging ability.”

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Publication: Optics Letters
Issue/Year: Vol. 45, Issue 9, pp. 2584-2587 (2020)
DOI: 10.1364/OL.389946

Fast calculation of computer-generated hologram of line-drawn objects without FFT

Author(s):

Nishitsuji, Takashi; Shimobaba, Tomoyoshi; Kakue, Takashi & Ito, Tomoyoshi

Abstract:

“Although holographic display technology is one of the most promising three-dimensional (3D) display technologies for virtual and augmented reality, the enormous computational effort required to produce computer-generated holograms (CGHs) to digitally record and display 3D images presents a significant roadblock to the implementation of this technology. One of the most effective methods to implement fast CGH calculations is a diffraction calculation (e.g., angular spectrum diffraction) based on the fast-Fourier transform (FFT). Unfortunately, the computational complexity increases with increasing CGH resolution, which is what determines the size of a 3D image. Therefore, enormous calculations are still required to display a reasonably sized 3D image, even for a simple 3D image. To address this issue, we propose herein a fast CGH algorithm for 3D objects comprised of line-drawn objects at layers of different depths. An aperture formed from a continuous line at a single depth can be regarded as a series of aligned point sources of light, and the wavefront converges for a sufficiently long line. Thus, a CGH of a line-drawn object can be calculated by synthesizing converged wavefronts along the line. Numerical experiments indicate that, compared with the FFT-based method, the proposed method offers a factor-56 gain in speed for calculating 16-k-resolution CGHs from 3D objects composed of twelve line-drawn objects at different depths.”

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Publication: Optics Express
Issue/Year: Optics Express, Volume 28; Number 11; Pages 15907; 2020
DOI: 10.1364/oe.389778

Learning-based super interpolation and extrapolation for speckled image reconstruction

Author(s):

Li, Huanhao; Yu, Zhipeng; Luo, Yunqi; Cheng, Shengfu; Wang, Lihong V.; Zheng, Yuanjin & Lai, Puxiang

Abstract:

“Speckles arise when coherent light interacts with biological tissues. Information retrieval from speckles is desired yet challenging, requiring understanding or mapping of the multiple scattering process, or reliable capability to reverse or compensate for the scattering-induced phase distortions. In whatever situation, insufficient sampling of speckles undermines the encoded information, impeding successful object reconstruction from speckle patterns. In this work, we propose a deep learning method to combat the physical limit: the sub-Nyquist sampled speckles ( 14 below the Nyquist criterion) are interpolated up to a well-resolved level (1024 times more pixels to resolve the same FOV) with smoothed morphology fine-textured. More importantly, the lost information can be retraced, which is impossible with classic interpolation or any existing methods. The learning network inspires a new perspective on the nature of speckles and a promising platform for efficient processing or deciphering of massive scattered optical signals, enabling widefield high-resolution imaging in complex scenarios.”

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Publication: arXiv
Issue/Year: arXiv, 2020
DOI: https://arxiv.org/abs/2005.00834v1

Hybrid multifocal structured illumination microscopy with enhanced lateral resolution and axial localization capability

Author(s):

Wang, Zhaojun; Cai, Yanan; Qian, Jia; Zhao, Tianyu; Liang, Yansheng; Dan, Dan; Lei, Ming & Yao, Baoli

Abstract:

“Super-resolution (SR) fluorescence microscopy that breaks through the diffraction barrier has drawn great interest in biomedical research. However, obtaining a high precision three-dimensional distribution of the specimen in a short time still remains a challenging task for existing techniques. In this paper, we propose a super-resolution fluorescence microscopy with axial localization capability by combining multifocal structured illumination microscopy with a hybrid detection PSF composed of a Gaussian PSF and a double-helix PSF. A modified reconstruction scheme is presented to accommodate the new hybrid PSF. This method can not only recover the lateral super-resolution image of the specimen but also retain the specimen’s depth map within a range of 600 nm with an axial localization precision of 20.8 nm. The performance of this approach is verified by testing fluorescent beads and tubulin in 293-cells. The developed microscope is well suited for observing the precise 3D distribution of thin specimens.”

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Publication: Biomedical Optics Express
Issue/Year: Biomedical Optics Express, Volume 11; Number 6; Pages 3058; 2020
DOI: 10.1364/boe.391024
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