Metamachines of pluripotent colloids

Author(s):

Aubret, Antoine; Martinet, Quentin & Palacci, Jeremie

Abstract:

“Machines enabled the Industrial Revolution and are central to modern technological progress: A machine’s parts transmit forces, motion, and energy to one another in a predetermined manner. Today’s engineering frontier, building artificial micromachines that emulate the biological machinery of living organisms, requires faithful assembly and energy consumption at the microscale. Here, we demonstrate the programmable assembly of active particles into autonomous metamachines using optical templates. Metamachines, or machines made of machines, are stable, mobile and autonomous architectures, whose dynamics stems from the geometry. We use the interplay between anisotropic force generation of the active colloids with the control of their orientation by local geometry. This allows autonomous reprogramming of active particles of the metamachines to achieve multiple functions. It permits the modular assembly of metamachines by fusion, reconfiguration of metamachines and, we anticipate, a shift in focus of self-assembly towards active matter and reprogrammable materials.”

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Publication: Nature Communications
Issue/Year: Nature Communications, Volume 12; Number 1; 2021
DOI: 10.1038/s41467-021-26699-6

Faster generation of holographic video of 3-D scenes with a Fourier spectrum-based NLUT method

Author(s):

Cao, Hongkun; Jin, Xin; Ai, Lingyu & Kim, Eun-Soo

Abstract:

“In this article, a new type of Fourier spectrum-based novel look-up table (FS-NLUT) method is proposed for the faster generation of holographic video of three-dimensional (3-D) scenes. This proposed FS-NLUT method consists of principal frequency spectrums (PFSs) which are much smaller in size than the principal fringe patterns (PFPs) found in the conventional NLUT-based methods. This difference in size allows for the number of basic algebraic operations in the hologram generation process to be reduced significantly. In addition, the fully one-dimensional (1-D) calculation framework of the proposed method also allows for a significant reduction of overall hologram calculation time. In the experiments, the total number of basic algebraic operations needed for the proposed FS-NLUT method were found to be reduced by 81.23% when compared with that of the conventional 1-D NLUT method. In addition, the hologram calculation times of the proposed method, when implemented in the CPU and the GPU, were also found to be 60% and 66% faster than that of the conventional 1-D NLUT method, respectively. It was also confirmed that the proposed method implemented with two GPUs can generate a holographic video of a test 3-D scene in real-time (>24f/s).”

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Publication: Optics Express
Issue/Year: Optics Express, Volume 29; Number 24; Pages 39738; 2021
DOI: 10.1364/oe.442267

Vector optical field with the polarization varying along an arbitrary circular trajectory on the Poincar’e sphere

Author(s):

Lü, Jia-Qi; Wang, Wen-Yue; Cheng, Tian-Yu; Lu, Zhi-Wei & Liu, Shuo

Abstract:

“As an inherent feature of vector optical field, the spatial distribution of polarization brings additional degrees of freedom to engineer the optical field and control the interaction between light and matters. Here we focus on the variation of polarization in single vector optical field, which can be defined by the trajectory on the Poincaré sphere. Based on the amplitude-phase-polarization joint modulation method we propose, vector optical field, whose variation of polarization follows arbitrary circular trajectory on the Poincaré sphere, can be generated. Moreover, the tightly focusing behaviors of the vector optical fields with the polarization varying along parallel circles on the Poincaré sphere are compared. Relations between the circular trajectory and the central intensity of the hollow focal field are concluded.”

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Publication: Optics Express
Issue/Year: Optics Express, Volume 29; Number 24; Pages 39718; 2021
DOI: 10.1364/oe.441809

Speckle-free holography with partially coherent light sources and camera-in-the-loop calibration

Author(s):

Peng, Yifan; Choi, Suyeon; Kim, Jonghyun & Wetzstein, Gordon

Abstract:

“Computer-generated holography (CGH) holds transformative potential for a wide range of applications, including direct-view, virtual and augmented reality, and automotive display systems. While research on holographic displays has recently made impressive progress, image quality and eye safety of holographic displays are fundamentally limited by the speckle introduced by coherent light sources. Here, we develop an approach to CGH using partially coherent sources. For this purpose, we devise a wave propagation model for partially coherent light that is demonstrated in conjunction with a camera-in-the-loop calibration strategy. We evaluate this algorithm using light-emitting diodes (LEDs) and superluminescent LEDs (SLEDs) and demonstrate improved speckle characteristics of the resulting holograms compared with coherent lasers. SLEDs in particular are demonstrated to be promising light sources for holographic display applications, because of their potential to generate sharp and high-contrast two-dimensional (2D) and 3D images that are bright, eye safe, and almost free of speckle.”

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Publication: Science Advances
Issue/Year: Science Advances, Volume 7; Number 46; 2021
DOI: 10.1126/sciadv.abg5040

Realization and measurement of Airy transform of Gaussian vortex beams

Author(s):

Zhou, Lu; Zhou, Tong; Wang, Fei; Li, Xia; Chen, Ruipin; Zhou, Yimin & Zhou, Guoquan

Abstract:

“Airy transformation is a useful technique to modulate amplitude and phase of a light beam, which has important applications in particle trapping/manipulation, optical communications and optical imaging. However, most of the studies only focused on the Airy transform of Gaussian beams and other vortex-free beams in the past. In this paper, the Airy transform of Gaussian vortex beams, which are the most common vortex beams, is investigated. A universal analytical expression of the Gaussian vortex beams with topological charge (TC) m passing through an Airy transform optical system is derived. We carry out a detailed study on the output beams’ characteristics after the Airy transform of the Gaussian vortex beams with m = ± 1 and ± 2. The analytical expressions for the centroid, the beam spot size, the divergence angle and the beam propagation factor of the output beams are derived. The effects of the Airy control parameters and the TC on the normalized intensity distribution, the phase distribution, the centroid, the beam spot size and the beam propagation factor of the output beams are investigated both theoretically and experimentally. The experimental results agree reasonably well with the theoretical results which illustrate the properties of Airy transform of the Gaussian vortex beams.”

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Publication: Optics and Laser Technology
Issue/Year: Optics and Laser Technology, Volume 143; Pages 107334; 2021
DOI: 10.1016/j.optlastec.2021.107334

Clustering-based CLEAN algorithm in ghost imaging with sparse spatial frequencies

Author(s):

Chang, Chen; Wu, Guohua; Yang, Dongyue; Yin, Longfei & Luo, Bin

Abstract:

“When insufficient samples in the spatial frequency domain could be effectively compensated by the modified CLEAN algorithm, a novel aperture-synthetic scheme of ghost imaging takes advantage of a superior speed of modulation and an enhancement on the spatial resolution. However, there still exist some imperfections in the modified CLEAN reconstructions, such as the fact that some omitted scatter noise still remains or the object contour may be incomplete. Therefore, we optimize the modified CLEAN algorithm by proposing a density clustering algorithm to overcome these drawbacks and improve the visual quality.”

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Publication: Optics Express
Issue/Year: Optics Express, Volume 29; Number 23; Pages 38841; 2021
DOI: 10.1364/oe.440497

Axial resolution enhancement for planar Airy beam light-sheet microscopy via the complementary beam subtraction method

Author(s):

Liu, Chao; Yu, Xianghua; Bai, Chen; Li, Xing; Zhou, Yuan; Yan, Shaohui; Min, Junwei; Dan, Dan; Li, Runze; Gu, Shuangyu & Yao, Baoli

Abstract:

“Airy beam light-sheet illumination can extend the field of view (FOV) of light-sheet fluorescence microscopy due to the unique propagation properties of non-diffraction and self-acceleration. However, the side lobes create undesirable out-of-focus background, leading to poor axial resolution and low image contrast. Here, we propose an Airy complementary beam subtraction (ACBS) method to improve the axial resolution while keeping the extended FOV. By scanning the optimized designed complementary beam that has two main lobes (TML), the generated complementary light-sheet has almost identical intensity distribution to that of the planar Airy light-sheet except for the central lobe. Subtraction of the two images acquired by double exposure respectively using the planar Airy light-sheet and the planar TML light-sheet can effectively suppress the influence of the out-of-focus background. The axial resolution improves from ∼4µm to 1.2 µm. The imaging performance was demonstrated by imaging specimens of aspergillus conidiophores and GFP labeled mouse brain section. The results show that the ACBS method enables the Airy beam light-sheet fluorescence microscopy to obtain better imaging quality.”

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Publication: Applied Optics
Issue/Year: Applied Optics, Volume 60; Number 32; Pages 10239; 2021
DOI: 10.1364/ao.441070