Generation of controllable spectrum in multiple positions from speckle patterns

Author(s):

Li, Haoran; Wu, Xiaoyan; Liu, Guodong; Vinu, R. V.; Wang, Xiaoyan; Chen, Ziyang & Pu, Jixiong

Abstract:

“Feedback-based wavefront shaping has been proposed to modulate the speckle field generated by coherent light transmitting through scattering media. Different from a monochromatic light, a colorful speckle pattern is generated when polychromatic light transmits through scattering media. Although single-position spectrum modulation has been realized, multiple-position spectrum modulation is a much more complicated problem. Based on non-dominated sorting genetic algorithm II (NSGA2), we design a step-by-step strategy to solve this problem. The results show that modulated spectra in two spatial positions with controllable spectral shape, range and magnitude can be achieved. This research is expected to be applied in the field of adaptive spectral control ranging from advanced spectral filtering to optical fiber dispersion and multi-spectral imaging.”

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Publication: Optics & Laser Technology
Issue/Year: Optics & Laser Technology, Volume 149; Pages 107820; 2022
DOI: 10.1016/j.optlastec.2021.107820

Speckle reduction in holographic display with partially spatial coherent illumination

Author(s):

Zhao, Zijie; Duan, Junyi & Liu, Juan

Abstract:

“A method of holographic reconstruction under partially spatial coherent illumination with different degree of coherence is proposed to suppress speckle noise based on theoretical analysis. The core factor of speckle reduction based on partially spatial coherent light is convolution operation in CGH reconstruction process. Numerical simulations and optical experiments are both performed to verify the proposed theory. The results reconstructed by proposed and traditional method are compared, and the speckle contrasts can be reduced to 0.05 and 0.08 at most in Fresnel and Fraunhofer zone respectively. The image quality is obviously improved. This method can provide further applications for three-dimensional holographic display, beam shaping and coherence degree modulation techniques.”

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Publication: Optics Communications
Issue/Year: Optics Communications, Volume 507; Pages 127604; 2022
DOI: 10.1016/j.optcom.2021.127604

Singularities splitting phenomenon for the superposition of hybrid orders structured lights and the corresponding interference discrimination method

Author(s):

Mao, Baiwei; Liu, Yange; Chang, Wenzhe; Chen, Liang; Feng, Mao; Guo, Huiyi; He, Jiangyong & Wang, Zhi

Abstract:

“It is the basic characteristic of pure vortex light

that there is a phase singularity at the origin. Such a sin-

gularity may be multiple degenerate, which determines the

order of vortex light. Singularities splitting phenomenon

means that singularities no longer concentrate at the origin

but distribute around the space, usually occurring in

impure vortex light. In this paper, we demonstrate the

singularities splitting phenomenon and propose an anal-

ysis method, based on which one may rapidly estimate the

modal components of impure vortex light. As two common

singularity discrimination methods, the spiral and fork

wire interference patterns are compared in distinguishing

splitting singularities. The most widely used spiral inter-

ference pattern is revealed to be the worst form because of

the low resolution. Instead, the fork wire interference

pattern is with higher and easily adjusted resolution. 1‰

impurity is still able to be distinguished through fork wire

interference patterns in the experiment.”

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Publication: Nanophotonics
Issue/Year: Nanophotonics, Volume 0; Number 0; 2022
DOI: 10.1515/nanoph-2021-0814

Scalability of all-optical neural networks based on spatial light modulators

Author(s):

Ying Zuo, Zhao Yujun, You-Chiuan Chen, Shengwang Du & Liu, Junwei

Abstract:

“Optical implementation of artificial neural networks has been attracting great attention due to its potential in parallel computation at speed of light. Although all-optical deep neural networks (AODNNs) with a few neurons have been experimentally demonstrated with acceptable errors re- cently, the feasibility of large scale AODNNs remains unknown because error might accumulate inevitably with increasing number of neurons and connections. Here, we demonstrate a scalable AODNN with programmable linear operations and tunable nonlinear activation functions. We ver- ify its scalability by measuring and analyzing errors propagating from a single neuron to the entire network. The feasibility of AODNNs is further confirmed by recognizing handwritten digits and fashions respectively.”

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Publication: Physical Review Applied
Issue/Year: Physical Review Applied, 2021
DOI: https://doi.org/10.1103/PhysRevApplied.15.054034

Precise position and angular control of optical trapping and manipulation via a single vortex-pair beam

Author(s):

Jisen Wen, Binjie Gao, Guiyuan Zhu, DadongLiu, Li-GangWang

Abstract:

“Optical trapping and manipulation using structured laser beams now attract increasing attention in many areas including biology, atomic science, and nanofabrication. Here we propose and demonstrate experimentally the use of a single vortex-pair beam in two-dimensional optical trapping and manipulation. Using the focal properties of such vortex-pair beams, we successfully manipulate two spherical microparticles simultaneously, and obtain the precise position-control on the microparticles by adjusting the off-axis parameter of the vortex-pair beam. Furthermore, we also realize the high-precision angular-controllable rotation of cylindrical microrods by rotating the initial phase structure of such vortex-pair beams, which is like an optical wrench due to two focused bright spots at the focal plane of objective lens. Our experimental result provides an alternative manipulation of microparticles and may have potential applications in biological area, and optically driven micromachines or motors.”

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Publication: Optics and Lasers in Engineering
Issue/Year: Optics and Lasers in Engineering, Volume 148, 106773 (2022)
DOI: 10.1016/j.optlaseng.2021.106773

Dual-task convolutional neural network based on the combination of the U-Net and a diffraction propagation model for phase hologram design with suppressed speckle noise

Author(s):

Sun, Xiuhui; Mu, Xingyu; Xu, Cheng; Pang, Hui; Deng, Qiling; Zhang, Ke; Jiang, Haibo; Du, Jinglei; Yin, Shaoyun & Du, Chunlei

Abstract:

“In this paper, a dual-task convolutional neural network based on the combination of the U-Net and a diffraction propagation model is proposed for the design of phase holograms to suppress speckle noise of the reconstructed images. By introducing a Fresnel transmission layer, based on angular spectrum diffraction theory, as the diffraction propagation model and incorporating it into U-Net as the output layer, the proposed neural network model can describe the actual physical process of holographic imaging, and the distributions of both the light amplitude and phase can be generated. Afterwards, by respectively using the Pearson correlation coefficient (PCC) as the loss function to modulate the distribution of the amplitude, and a proposed target-weighted standard deviation (TWSD) as the loss function to limit the randomness and arbitrariness of the reconstructed phase distribution, the dual tasks of the amplitude reconstruction and phase smoothing are jointly solved, and thus the phase hologram that can produce high quality image without speckle is obtained. Both simulations and optical experiments are carried out to confirm the feasibility and effectiveness of the proposed method. Furthermore, the depth of field (DOF) of the image using the proposed method is much larger than that of using the traditional Gerchberg-Saxton (GS) algorithm due to the smoothness of the reconstructed phase distribution, which is also verified in the experiments. This study provides a new phase hologram design approach and shows the potential of neural networks in the field of the holographic imaging and more.”

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Publication: Optics Express
Issue/Year: Optics Express, Volume 30; Number 2; Pages 2646; 2022
DOI: 10.1364/oe.440956

Discretized continuous quantum-mechanical observables that are neither continuous nor discrete

Author(s):

Thais L. Silva, Łukasz Rudnicki, Daniel S. Tasca, and Stephen P. Walborn

Abstract:

“Most of the fundamental characteristics of quantum mechanics, such as nonlocality and contextuality, are manifest in discrete, finite-dimensional systems. However, many quantum information tasks that exploit these properties cannot be directly adapted to continuous variable systems. To access these quantum features, continuous quantum variables can be made discrete by binning together their different values, resulting in observables with a finite number, d, of outcomes. While direct measurement indeed confirms their manifestly discrete character, here we employ a salient feature of quantum physics known as mutual unbiasedness to show that such coarse-grained observables are in a sense neither continuous nor discrete. Depending on d, the observables can reproduce either the discrete or the continuous behavior, or neither. To illustrate these results, we present an example for the construction of such measurements and employ it in an optical experiment confirming the existence of four mutually unbiased measurements with d=3 outcomes in a continuous variable system, surpassing the number of mutually unbiased continuous variable observables.”

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Publication: Physical Review Research
Issue/Year: Physical Review Research, Volume 4; Number 1; Pages 013060; 2022
DOI: 10.1103/physrevresearch.4.013060

Polygon-based computer-generated holography: a review of fundamentals and recent progress [Invited]

Author(s):

Zhang, Yaping; Fan, Houxin; Wang, Fan; Gu, Xianfeng; Qian, Xiaofan & Poon, Ting-Chung

Abstract:

“In this review paper, we first provide comprehensive tutorials on two classical methods of polygon-based computer-

generated holography: the traditional method (also called the fast-Fourier-transform-based method) and the

analytical method. Indeed, other modern polygon-based methods build on the idea of the two methods. We will

then present some selective methods with recent developments and progress and compare their computational

reconstructions in terms of calculation speed and image quality, among other things. Finally, we discuss and pro-

pose a fast analytical method called the fast 3D affine transformation method, and based on the method, we present

a numerical reconstruction of a computer-generated hologram (CGH) of a 3D surface consisting of 49,272 pro-

cessed polygons of the face of a real person without the use of graphic processing units; to the best of our knowledge,

this represents a state-of-the-art numerical result in polygon-based computed-generated holography. Finally, we

also show optical reconstructions of such a CGH and another CGH of the Stanford bunny of 59,996 polygons with

31,724 processed polygons after back-face culling. We hope that this paper will bring out some of the essence of

polygon-based computer-generated holography and provide some insights for future research.”

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Publication: Applied Optics
Issue/Year: Applied Optics, Volume 61; Number 5; Pages B363; 2022
DOI: 10.1364/ao.444973

Improving Multiphoton Microscopy by Combining Spherical Aberration Patterns and Variable Axicons

Author(s):

Bueno, J.M.; Hernández, G.; Skorsetz, M.; Artal, P.

Abstract:

“Multiphoton (MP) microscopy is a well-established method for the non-invasive imaging of biological tissues. However, its optical sectioning capabilities are reduced due to specimen-induced aberrations. Both the manipulation of spherical aberration (SA) and the use of axicons have been reported to be useful techniques to bypass this limitation. We propose the combination of SA patterns and variable axicons to further improve the quality of MP microscopy images. This approach provides enhanced images at different depth locations whose quality is better than those corresponding to the use of SA or axicons separately. Thus, the procedure proposed herein facilitates the visualization of details and increases the depth observable at high resolution.”

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Publication: Photonics
Issue/Year: Photonics, Volume 8; Number 12; Pages 573; 2021
DOI: 10.3390/photonics8120573

Neural 3D holography

Author(s):

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

Abstract:

“Holographic near-eye displays promise unprecedented capabilities for virtual and augmented reality (VR/AR) systems. The image quality achieved by current holographic displays, however, is limited by the wave propagation models used to simulate the physical optics. We propose a neural network-parameterized plane-to-multiplane wave propagation model that closes the gap between physics and simulation. Our model is automatically trained using camera feedback and it outperforms related techniques in 2D plane-to-plane settings by a large margin. Moreover, it is the first network-parameterized model to naturally extend to 3D settings, enabling high-quality 3D computer-generated holography using a novel phase regularization strategy of the complex-valued wave field. The efficacy of our approach is demonstrated through extensive experimental evaluation with both VR and optical see-through AR display prototypes.”

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Publication: ACM Transactions on Graphics
Issue/Year: ACM Transactions on Graphics, Volume 40; Number 6; Pages 1–12; 2021
DOI: 10.1145/3478513.3480542
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