High-resolution surface plasmon resonance holographic microscopy based on symmetrical excitation

Author(s):

Dou, Jiazhen; Dong, Chen; Dai, Siqing; Mi, Jingyu; Luo, Xiangyuan; Di, Jianglei; Zhang, Jiwei & Zhao, Jianlin

Abstract:

“Surface plasmon resonance holographic microscopy (SPRHM) is able to simultaneously obtain the amplitude- and phase-contrast surface plasmon resonance (SPR) images, showing great potentials in imaging near-field targets with high sensitivity. However, suffered by the decaying length of surface plasmon wave which can be as long as tens of microns, the spatial resolution of SPRHM is lower than that of traditional holographic microscopy. In this work, we propose to enhance the spatial resolution in SPRHM by exciting surface plasmon resonance in two symmetrical directions and detecting the complex amplitudes of the reflected light symmetrically. Through the Fourier analysis of the recorded composite hologram, the reconstruction schemes for high-resolution amplitude- and phase-contrast SPR images are established, respectively. The feasibility and advantages of the proposed method is verified by numerical simulations and experimental demonstrations of small-size particles and micro-structures.”

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Publication: Optics and Lasers in Engineering
Issue/Year: Optics and Lasers in Engineering, Volume 153; Pages 107000; 2022
DOI: 10.1016/j.optlaseng.2022.107000

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

Control of trion-to-exciton conversion in monolayer WS2 by orbital angular momentum of light

Author(s):

Kesarwani, Rahul; Simbulan, Kristan Bryan; Huang, Teng-De; Chiang, Yu-Fan; Yeh, Nai-Chang; Lan, Yann-Wen & Lu, Ting-Hua

Abstract:

“Controlling the density of exciton and trion quasiparticles in monolayer two-dimensional (2D) materials at room temperature by nondestructive techniques is highly desired for the development of future optoelectronic devices. Here, the effects of different orbital angular momentum (OAM) lights on monolayer tungsten disulfide at both room temperature and low temperatures are investigated, which reveal simultaneously enhanced exciton intensity and suppressed trion intensity in the photoluminescence spectra with increasing topological charge of the OAM light. In addition, the trion-to-exciton conversion efficiency is found to increase rapidly with the OAM light at low laser power and decrease with increasing power. Moreover, the trion binding energy and the concentration of unbound electrons are estimated, which shed light on how these quantities depend on OAM. A phenomenological model is proposed to account for the experimental data. These findings pave a way toward manipulating the exciton emission in 2D materials with OAM light for optoelectronic applications.”

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Publication: Science Advances
Issue/Year: Science Advances, Volume 8; Number 13; 2022
DOI: 10.1126/sciadv.abm0100

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

Adaptive Detection of Wave Aberrations Based on the Multichannel Filter

Author(s):

Khorin, Pavel A.; Porfirev, Alexey P. & Khonina, Svetlana N.

Abstract:

“An adaptive method for determining the type and magnitude of aberration in a wide range is proposed on the basis of an optical processing of the analyzed wavefront using a multichannel filter matched to the adjustable Zernike phase functions. The approach is based on an adaptive (or step-by-step) compensation of wavefront aberrations based on a dynamically tunable multichannel filter implemented on a spatial light modulator. For adaptive filter adjustment, a set of criteria is proposed that takes into account not only the magnitude of the correlation peak, but also the maximum intensity, compactness, and orientation of the distribution in each diffraction order. The experimental results have shown the efficiency of the proposed approach for detecting wavefront aberrations in a wide range (from 0.1 λ to λ).”

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Publication: Photonics
Issue/Year: Photonics, Volume 9; Number 3; Pages 204; 2022
DOI: 10.3390/photonics9030204

Varifocal diffractive lenses for multi-depth microscope imaging

Author(s):

Reda, Francesco; Salvatore, Marcella; Borbone, Fabio; Maddalena, Pasqualino; Ambrosio, Antonio & Oscurato, Stefano Luigi

Abstract:

“Flat optical elements enable the realization of ultra-thin devices able to either reproduce or overcome the functionalities of standard bulky components. The fabrication of these elements involves the structuration of material surfaces on the light wavelength scale, whose geometry has to be carefully designed to achieve the desired optical functionality. In addition to the limits imposed by lithographic design-performance compromises, their optical behavior cannot be accurately tuned afterward, making them difficult to integrate in dynamic optical systems. Here we show the realization of fully reconfigurable flat varifocal diffractive lens, which can be in-place realized, erased and reshaped directly on the surface of an azopolymer film by an all-optical holographic process. Integrating the lens in the same optical system used as standard refractive microscope, results in a hybrid microscope capable of multi-depth object imaging. Our approach demonstrates that reshapable flat optics can be a valid choice to integrate, or even substitute, modern optical systems for advanced functionalities.”

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Publication: Optics Express
Issue/Year: Optics Express, Volume 30; Number 8; Pages 12695; 2022
DOI: 10.1364/oe.455520

Parametric characterization of ground surfaces with laser speckles

Author(s):

León Schweickhardt, Andreas Tausendfreund, Dirk Stöbener, and Andreas Fischer

Abstract:

“With well-known speckle measurement techniques, the root mean square height as well as the autocorrelation length of isotropic surfaces can be determined quickly and over a large area of interest. Beyond that, the present article studies the speckle-based measurement of anisotropic surfaces. For this purpose, a measurement setup and evaluation algorithm are presented that enable the characterization of unidirectionally anisotropic surfaces machined by grinding. As a result, four measurands are obtained from one speckle image: the machining direction, the autocorrelation length perpendicular to the machining direction, as well as two root mean square roughness parameters parallel and perpendicular to the machining direction. The first two measurands are obtained from a two-dimensional fast Fourier transform of the diffraction pattern resulting from the unidirectional tool marks and the latter two by a bidirectional evaluation of the speckle contrast. In addition to measurements on physical reference samples, a spatial light modulator is used to create a large number of surface topographies with known model parameters in order to quantify the measurement uncertainty.”

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Publication: Optics Express
Issue/Year: Optics Express, Volume 30; Number 8; Pages 12615; 2022
DOI: 10.1364/oe.454741

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.”

Link to Publications Page

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