Three-dimensional wide-field fluorescence microscopy for transcranial mapping of cortical microcirculation

Author(s):

Zhou, Quanyu; Chen, Zhenyue; Liu, Yu-Hang; El Amki, Mohamad; Glück, Chaim; Droux, Jeanne; Reiss, Michael; Weber, Bruno; Wegener, Susanne & Razansky, Daniel

Abstract:

“Wide-field fluorescence imaging is an indispensable tool for studying large-scale biodynamics. Limited space-bandwidth product and strong light diffusion make conventional implementations incapable of high-resolution mapping of fluorescence biodistribution in three dimensions. We introduce a volumetric wide-field fluorescence microscopy based on optical astigmatism combined with fluorescence source localization, covering 5.6×5.6×0.6 mm^3 imaging volume. Two alternative configurations are proposed exploiting multifocal illumination or sparse localization of point emitters, which are herein seamlessly integrated in one system. We demonstrate real-time volumetric mapping of the murine cortical microcirculation at capillary resolution without employing cranial windows, thus simultaneously delivering quantitative perfusion information across both brain hemispheres. Morphological and functional changes of cerebral vascular networks are further investigated after an acute ischemic stroke, enabling cortex-wide observation of concurrent collateral recruitment events occurring on a sub-second scale. The reported technique thus offers a wealth of unmatched possibilities for non- or minimally invasive imaging of biodynamics across scales.”

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Publication: Nature Communications
Issue/Year: Nature Communications, Volume 13; Number 1; Pages 1–11; 2022
DOI: 10.1038/s41467-022-35733-0

Ultrafast Transverse Modulation of Free Electrons by Interaction with Shaped Optical Fields

Author(s):

Madan, Ivan; Leccese, Veronica; Mazur, Adam; Barantani, Francesco; LaGrange, Thomas; Sapozhnik, Alexey; Tengdin, Phoebe M.; Gargiulo, Simone; Rotunno, Enzo; Olaya, Jean-Christophe; Kaminer, Ido; Grillo, Vincenzo; de Abajo, F. Javier Garcia; Carbone, Fabrizio & Vanacore, Giovanni Maria

Abstract:

“Spatiotemporal electron-beam shaping is a bold frontier of electron microscopy. Over the past decade, shaping methods evolved from static phase plates to low-speed electrostatic and magnetostatic displays. Recently, a swift change of paradigm utilizing light to control free electrons has emerged. Here, we experimentally demonstrate arbitrary transverse modulation of electron beams without complicated electron-optics elements or material nanostructures, but rather using shaped light beams. On-demand spatial modulation of electron wavepackets is obtained via inelastic interaction with transversely shaped ultrafast light fields controlled by an external spatial light modulator. We illustrate this method for the cases of Hermite-Gaussian and Laguerre-Gaussian modulation and discuss their use in enhancing microscope sensitivity. Our approach dramatically widens the range of patterns that can be imprinted on the electron profile and greatly facilitates tailored electron-beam shaping.”

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Publication: ACS Photonics
Issue/Year: ACS Photonics, 2022
DOI: 10.1021/acsphotonics.2c00850

Holographic Glasses for Virtual Reality

Author(s):

JONGHYUN KIM, NVIDIA, USA and Stanford University, USA
MANU GOPAKUMAR, SUYEON CHOI, AND YIFAN PENG, Stanford University, USA
WARD LOPES, NVIDIA, USA
GORDON WETZSTEIN, Stanford University, USA

Abstract:

“We resent Holographic Glasses, a holographic near-eye display system with an eyeglasses-like form factor for virtual reality. Holographic Glasses are composed of a pupil-replicating waveguide,
a spatial light modulator, and a geometric phase lens to create holographic images in a lightweight
and thin form factor. The proposed design can deliver full-color 3D holographic images using an optical stack of 2.5 mm thickness. A novel pupil-high-order gradient descent algorithm is presented for the correct phase calculation with the user’s varying pupil size. We implement benchtop and wearable prototypes for testing. Our binocular wearable prototype supports 3D focus cues and provides a diagonal field of view of 22.8? with a 2.3 mm static eye box and additional capabilities of dynamic eye box with beam steering, while weighing only 60 g excluding the driving board.”

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Publication: Association for Computing Machinery
Issue/Year: Association for Computing Machinery, 2022

Accommodative holography: improving accommodation response for perceptually realistic holographic displays

Author(s):

Kim, Dongyeon; Nam, Seung-Woo; Lee, Byounghyo; Seo, Jong-Mo & Lee, Byoungho

Abstract:

“Holographic displays have gained unprecedented attention as next-generation virtual and augmented reality applications with recent achievements in the realization of a high-contrast image through computer-generated holograms (CGHs). However, these holograms show a high energy concentration in a limited angular spectrum, whereas the holograms with uniformly distributed angular spectrum suffer from a severe speckle noise in the reconstructed images. In this study, we claim that these two physical phenomena attributed to the existing CGHs significantly limit the support of accommodation cues, which is known as one of the biggest advantages of holographic displays. To support the statement, we analyze and evaluate various CGH algorithms with contrast gradients – a change of contrast over the change of the focal diopter of the eye – simulated based on the optical configuration of the display system and human visual perception models. We first introduce two approaches to improve monocular accommodation response in holographic viewing experience; optical and computational approaches to provide holographic images with sufficient contrast gradients. We design and conduct user experiments with our prototype of holographic near-eye displays, validating the deficient support of accommodation cues in the existing CGH algorithms and demonstrating the feasibility of the proposed solutions with significant improvements on accommodative gains.”

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Publication: ACM Transactions on Graphics
Issue/Year: ACM Transactions on Graphics, Volume 41; Number 4; Pages 1–15; 2022
DOI: 10.1145/3528223.3530147

Multi-beam heterodyne laser Doppler vibrometer based on a line-scan CMOS digital camera

Author(s):

Aranchuk, Vyacheslav; Kasu, Ramachandran; Li, Junrui; Aranchuk, Ina & Hickey, Craig

Abstract:

“Multi-beam laser Doppler vibrometers (MB-LDVs) have an advantage over scanning single-beam laser Doppler vibrometers (LDVs) due to the reduction in measurement time and their ability to measure non-stationary and transient events. However, the number of simultaneously interrogated points in current MB-LDVs is limited due to the complexity of the electronic hardware, which increases with the number of measurement channels. Recent developments of high-speed line-scan CMOS cameras suggest that their use in MB-LDVs can reduce the hardware complexity and increase the number of measurement channels. We developed a MB-LDV based on a digital line-scan CMOS camera that simultaneously measures vibrations on a linear array of 99 points. The experimental setup and performance of the developed MB-LDV are discussed in this paper.”

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Publication: Appl. Opt.
Issue/Year: Appl. Opt., Volume 61; Number 20; Pages 5876–5883; 2022
DOI: 10.1364/AO.461368

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
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