Flexible rotation of transverse optical field for 2D self-accelerating beams with a designated trajectory

Author(s):

Li, Zongtao; Cao, Kai; Li, Jiasheng; Tang, Yong; Ding, Xinrui & Yu, Binhai

Abstract:

“Self-accelerating beams have the unusual ability to remain diffraction-free while undergo the transverse shift during the free-space propagation. We theoretically identify that the transverse optical field distribution of 2D self-accelerating beam is determined by the selection of the transverse Cartesian coordinates, when the caustic method is utilized for its trajectory design. Based on the coordinate-rotation method, we experimentally demonstrate a scheme to flexibly manipulate the rotation of transverse optical field for 2D self-accelerating beams under the condition of a designated trajectory. With this scheme, the transverse optical field can be rotated within a range of 90 degrees, especially when the trajectory of 2D self-accelerating beams needs to be maintained for free-space photonic interconnection.”

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Publication: Opto-Electronic Advances
Issue/Year: Opto-Electronic Advances, Volume 4; Number 3; Pages 20002101–20002115; 2021
DOI: 10.29026/oea.2021.200021

Comparative study on resolution enhancements in fluorescence-structured illumination Fresnel incoherent correlation holography

Author(s):

Jeon, Philjun; Kim, Jongwu; Lee, Heejung; Kwon, Hyuk-Sang & young Kim, Dug

Abstract:

“Fresnel incoherent correlation holography (FINCH) is a new approach for incoherent holography, which also has enhancement in the transverse resolution. Structured illumination microscopy (SIM) is another promising super-resolution technique. SI-FINCH, the combination of SIM and FINCH, has been demonstrated lately for scattering objects. In this study, we extended the application of SI-FINCH toward fluorescent microscopy. We have built a versatile multimodal microscopy system that can obtain images of four different imaging schemes: conventional fluorescence microscopy, FINCH, SIM, and SI-FINCH. Resolution enhancements were demonstrated by comparing the point spread functions (PSFs) of the four different imaging systems by using fluorescence beads of 1-μm diameter.”

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Publication: Optics Express
Issue/Year: Optics Express, Volume 29; Number 6; Pages 9231; 2021
DOI: 10.1364/oe.417206

Generation of Complex Transverse Energy Flow Distributions with Autofocusing Optical Vortex Beams

Author(s):

Khonina, Svetlana N.; Porfirev, Alexey P.; Ustinov, Andrey V. & Butt, Muhammad Ali

Abstract:

“Optical vortex (OV) beams are widely used for the generation of light fields with transverse energy flow inducing orbital motion of the nano- and microparticles in the transverse plane. Here, we present some new modifications of OV beams with autofocusing properties for shaping complex transverse energy flow distributions varying in space. The angular component of the complex amplitude of these beams is defined by the superpositions of OV beams with different topological charges. The proposed approach provides a convenient method to control the three-dimensional structure of the generated autofocusing OV beams. The control of the transverse distribution of an autofocusing beam provides a wide variety of generated fields with both rotating and periodic properties, which can be used in the field of laser manipulation and laser material processing. Thus, the obtained numerical results predict different types of motion of the trapped particles for the designed OV autofocusing beams. The experimental results agree with modeling results and demonstrate the principal possibility to shape such laser beams using spatial light modulators.”

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Publication: Micromachines
Issue/Year: Micromachines, Volume 12; Number 3; Pages 297; 2021
DOI: 10.3390/mi12030297

Tailored spectral rotation of vortex pulses by non-uniform spiral phase gratings

Author(s):

Liebmann, Max; Treffer, Alexander; Bock, Martin; Jurke, Mathias; Wallrabe, Ulrike & Grunwald, Rüdiger

Abstract:

“Previously we studied the spectral Gouy rotation as a specific rotational phenomenon of conical polychromatic light fields shaped by spiral gratings. The rotation of spectral anomalies around singularities results from accumulated spectrally dependent Gouy phase shift. We proposed to apply radially chirped spiral structures to obtain an axial modulation of the rotational characteristics. Here we present related experimental results with non-uniform spiral gratings which were programmed into a 10-Megapixel, phase-only, liquid-crystal-on-silicon (LCoS) spatial light modulator (SLM). A propagation-dependent variation of the Gouy rotation was indicated. More complex non-uniform geometries are considered.”

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Publication: SPIE Proceedings, Complex Light and Optical Forces XV;
Issue/Year: Proc. SPIE 11701, Complex Light and Optical Forces XV, 117010V, 2021
DOI: 10.1117/12.2578503

Rotational Doppler effect detection by LG beams with a nonzero radial index

Author(s):

Qiu, Song; Ren, Yuan; Liu, Tong; Li, Zhimeng; Liu, Zhengliang; Wang, Chen; Ding, You & Sha, Qimeng

Abstract:

“The capability to detect the rotational speed of non-cooperative targets in a long distance is a difficult problem to be solved. In recent years, vortex light provides a feasible solution for the measurement of rotational speed for its spiral phase and the orbital angular momentum. Laguerre-Gaussian (LG) mode, as the typical vortex beam, has been widely employed in rotational Doppler effect (RDE) experiments. Here, we show that the nonzero radial index LG beam not only has a specific physical meaning but also can enhance the light intensity and the amplitude of RDE frequency signal relative to a zero radial index LG beam. To this end, we theoretically analyze the reason of intensity enhancement of a nonzero radial index beam and verify the conclusion in a variable control experiment. Our study provides a new aspect of LG beams that can be considered in rotational speed detection based on RDE. It may produce an improvement of the detection range of rotating targets in practical applications.”

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Publication: Optics Express
Issue/Year: Optics Express, Volume 29; Number 7; Pages 10275; 2021
DOI: 10.1364/oe.421705

Holographic contact lens display that provides focusable images for eyes

Author(s):

Sano, Junpei & Takaki, Yasuhiro

Abstract:

“In this paper, we propose a holographic image generation technique for contact lens displays. The proposed technique employs a phase-only spatial light modulator (SLM), a holographic optical element (HOE) backlight, and a polarizer. The proposed holographic technique can generate 3D images apart from the contact lens displays. Therefore, the eyes can focus on the 3D images while simultaneously observing the real scene through the phase-only SLM and the HOE backlight, which provides see-through capability. A bench-top experimental system was constructed to verify the far-distance image generation capability and see-through function.”

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Publication: Optics Express
Issue/Year: Optics Express, Volume 29; Number 7; Pages 10568; 2021
DOI: 10.1364/oe.419604

Towards real-time photorealistic 3D holography with deep neural networks

Author(s):

Shi, Liang; Li, Beichen; Kim, Changil; Kellnhofer, Petr & Matusik, Wojciech

Abstract:

“The ability to present three-dimensional (3D) scenes with continuous depth sensation has a profound impact on virtual and augmented reality, human–computer interaction, education and training. Computer-generated holography (CGH) enables high-spatio-angular-resolution 3D projection via numerical simulation of diffraction and interference1. Yet, existing physically based methods fail to produce holograms with both per-pixel focal control and accurate occlusion. The computationally taxing Fresnel diffraction simulation further places an explicit trade-off between image quality and runtime, making dynamic holography impractical. Here we demonstrate a deep-learning-based CGH pipeline capable of synthesizing a photorealistic colour 3D hologram from a single RGB-depth image in real time. Our convolutional neural network (CNN) is extremely memory efficient (below 620 kilobytes) and runs at 60 hertz for a resolution of 1,920 × 1,080 pixels on a single consumer-grade graphics processing unit. Leveraging low-power on-device artificial intelligence acceleration chips, our CNN also runs interactively on mobile (iPhone 11 Pro at 1.1 hertz) and edge (Google Edge TPU at 2.0 hertz) devices, promising real-time performance in future-generation virtual and augmented-reality mobile headsets. We enable this pipeline by introducing a large-scale CGH dataset (MIT-CGH-4K) with 4,000 pairs of RGB-depth images and corresponding 3D holograms. Our CNN is trained with differentiable wave-based loss functions and physically approximates Fresnel diffraction. With an anti-aliasing phase-only encoding method, we experimentally demonstrate speckle-free, natural-looking, high-resolution 3D holograms. Our learning-based approach and the Fresnel hologram dataset will help to unlock the full potential of holography and enable applications in metasurface design, optical and acoustic tweezer-based microscopic manipulation, holographic microscopy and single-exposure volumetric 3D printing.”

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Publication: Nature
Issue/Year: Nature, Volume 591; Number 7849; Pages 234–239; 2021
DOI: 10.1038/s41586-020-03152-0

Long-range quasi-non-diffracting Gauss-Bessel beams in a few-cycle laser field

Author(s):

Stoyanov, Lyubomir; Zhang, Yinyu; Dreischuh, Alexander & Paulus, Gerhard G.

Abstract:

“Many applications ranging from nonlinear optics to material processing would benefit from pulsed ultrashort (quasi-)non-diffracting Gauss-Bessel beams (GBBs). Here we demonstrate a straightforward yet efficient method for generating such zeroth- and first-order GBBs using a single reflective spatial light modulator. Even in the sub-8-fs range there are no noticeable consequences for the measured pulse duration. The only effect is a weak “coloring” of the outer-lying satellite rings of the beams due to the spectrum spanning over more than 300 nm. The obtained beams have diffraction half-angles below 40 μrad and reach propagation distances in excess of 1.5 m.”

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Publication: Optics Express
Issue/Year: Optics Express, Volume 29; Number 7; Pages 10997; 2021
DOI: 10.1364/oe.419486

Tailoring a complex perfect optical vortex array with multiple selective degrees of freedom

Author(s):

Wang, Hao; Fu, Shiyao & Gao, Chunqing

Abstract:

“Optical vortex arrays (OVAs) have successfully aroused substantial interest from researchers for their promising prospects ranging from classical to quantum physics. Previous reported OVAs still show a lack of controllable dimensions which may hamper their applications. Taking an isolated perfect optical vortex (POV) as an array element, whose diameter is independent of its topological charge (TC), this paper proposes combined phase-only holograms to produce sophisticated POV arrays. The contributed scheme enables dynamically controllable multi-ring, TC, eccentricity, size, and the number of optical vortices (OVs). Apart from traditional single ring POV element, we set up a βg library to obtain optimized double ring POV element. With multiple selective degrees of freedom to be chosen, a series of POV arrays are generated which not only elucidate versatility of the method but also unravel analytical relationships between the set parameters and intensity patterns. More exotic structures are formed like the “Bear POV” to manifest the potential of this approach in tailoring customized structure beams. The experimental results show robust firmness with the theoretical simulations. As yet, these arrays make their public debut so far as we know, and will find miscellaneous applications especially in multi-microparticle trapping, large-capacity optical communications, novel pumping lasers and so on.”

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Publication: Optics Express
Issue/Year: Optics Express, Volume 29; Number 7; Pages 10811; 2021
DOI: 10.1364/oe.422301

A generalized iterative projection framework for pixel-super-resolved holographic imaging

Author(s):

Gao, Yunhui & Cao, Liangcai

Abstract:

“Lensless holographic imaging is challenged by the twin-image artifact due to the missing phase and the aliasing effect due to the undersampled measurement. Therefore, phase retrieval and pixel super-resolution (PSR) techniques serve as the essential ingredients for high-fidelity holographic imaging. In this work, we combine the two in a unified framework by formulating the PSR phase retrieval as a non-convex feasibility problem. An adaptive smoothing strategy for escaping local minima is introduced. Numerical and experimental results are presented and discussed. The proposed framework can be generalized to various physical settings, and is compatible with the state-of-the-art iterative projection algorithms.”

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Publication:
Issue/Year: , 2021
DOI: 10.1117/12.2577198
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