All-optical image identification with programmable matrix transformation

Author(s):

Li, Shikang; Ni, Baohua; Feng, Xue; Cui, Kaiyu; Liu, Fang; Zhang, Wei & Huang, Yidong

Abstract:

“An optical neural network is proposed and demonstrated with programmable matrix transformation and nonlinear activation function of photodetection (square-law detection). Based on discrete phase-coherent spatial modes, the dimensionality of programmable optical matrix operations is 30∼37, which is implemented by spatial light modulators. With this architecture, all-optical classification tasks of handwritten digits, objects and depth images are performed. The accuracy values of 85.0% and 81.0% are experimentally evaluated for MNIST (Modified National Institute of Standards and Technology) digit and MNIST fashion tasks, respectively. Due to the parallel nature of matrix multiplication, the processing speed of our proposed architecture is potentially as high as 7.4∼74 T FLOPs per second (with 10∼100 GHz detector).”

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Publication: Optics Express
Issue/Year: Optics Express, Volume 29; Number 17; Pages 26474; 2021
DOI: 10.1364/oe.430281

Non-spreading Bessel spatiotemporal optical vortices

Author(s):

Cao, Qian; Chen, Jian; Lu, Keyin; Wan, Chenhao; Chong, Andy & Zhan, Qiwen

Abstract:

“Non-spreading nature of Bessel spatiotemporal wavepackets is theoretically and experimentally investigated and orders of magnitude improvement in the spatiotemporal spreading has been demonstrated. The spatiotemporal confinement provided by the Bessel spatiotemporal wavepacket is further exploited to transport transverse orbital angular momentum through embedding spatiotemporal optical vortex into the Bessel spatiotemporal wavepacket, constructing a new type of wavepacket: Bessel spatiotemporal optical vortex. Both numerical and experimental results demonstrate that spatiotemporal vortex structure can be well maintained and confined through much longer propagation. High order spatiotemporal optical vortices can also be better confined in the spatiotemporal domain and prevented from further breaking up, overcoming a potential major obstacle for future applications of spatiotemporal vortex.”

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Publication: Science Bulletin
Issue/Year: Science Bulletin, 2021
DOI: 10.1016/j.scib.2021.07.031

Vision-correcting Holographic Display: Evaluation of Aberration Correcting Hologram

Author(s):

Kim, Dongyeon; Nam, Seung-Woo; Bang, Kiseung; Lee, Byounghyo; Lee, Seungjae; Jeong, Youngmo; Seo, Jongmo & Lee, Byoungho

Abstract:

“Vision-correcting displays are key to achieving physical and physiological comforts to the users with refractive errors. Among such displays are holographic displays, which can provide a high-resolution vision-adaptive solution with complex wavefront modulation. However, none of the existing hologram rendering techniques have considered the optical properties of the human eye nor evaluated the significance of vision correction. Here, we introduce vision-correcting holographic display and hologram acquisition that integrates user-dependent prescriptions and a physical model of the optics, enabling the correction of on-axis and off-axis aberrations. Experimental and empirical evaluations of the vision-correcting holographic displays show the competence of holographic corrections over the conventional vision correction solutions.”

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Publication: Biomedical Optics Express
Issue/Year: Biomedical Optics Express,Vol. 12, Issue 8, pp. 5179-5195, 2021
DOI: 10.1364/boe.433919

Fourier horizontal parallax only computer and digital holography of large size

Author(s):

Kozacki, Tomasz; Martinez-Carranza, Juan; kuko{l}owicz, Rafa{l} & Chlipa{l}a, Maksymilian

Abstract:

“Registration and reconstruction of high-quality digital holograms with a large view angle are intensive computer tasks since they require the space-bandwidth product (SBP) of the order of tens of gigapixels or more. This massive use of SBP severely affects the storing and manipulation of digital holograms. In order to reduce the computer burden, this work focuses on the generation and reconstruction of very large horizontal parallax only digital holograms (HPO-DHs). It is shown that these types of holograms can preserve high quality and large view angle in x direction while keeping a low use of SBP. This work first proposes a numerical technique that allows calculating very large HPO-DHs with large pixel size by merging the Fourier holography and phase added stereogram algorithm. The generated Fourier HPO-DHs enable accurate storing of holographic data from 3D objects. To decode the information contained in these Fourier HPO-DHs (FHPO-DHs), a novel angular spectrum (AS) technique that provides an efficient use of the SBP for reconstruction is proposed. Our reconstruction technique, which is called compact space bandwidth AS (CSW-AS), makes use of cylindrical parabolic waves that solve sampling issues of FHPO-DHs and AS. Moreover, the CSW-AS allows for implementing zero-padding for accurate wavefield reconstructions. Hence, suppression of aliased components and high spatial resolution is possible. Notably, the imaging chain of Fourier HPO-DH enables efficient calculation, reconstruction and storing of HPO holograms of large size. Finally, the accuracy and utility of the developed technique is proved by both numerical and optical reconstructions.”

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Publication: Optics Express
Issue/Year: Optics Express, Volume 29; Number 12; Pages 18173; 2021
DOI: 10.1364/oe.421186

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

Foveated near-eye display using computational holography

Author(s):

Cem, Ali; Hedili, M. Kivanc; Ulusoy, Erdem & Urey, Hakan

Abstract:

“Holographic display is the only technology that can offer true 3D with all the required depth cues. Holographic head-worn displays (HWD) can provide continuous depth planes with the correct stereoscopic disparity for a comfortable 3D experience. Existing HWD approaches have small field-of-view (FOV) and small exit pupil size, which are limited by the spatial light modulator (SLM). Conventional holographic HWDs are limited to about 20° × 11° FOV using a 4 K SLM panel and have fixed FOV. We present a new optical architecture that can overcome those limitations and substantially extend the FOV supported by the SLM. Our architecture, which does not contain any moving parts, automatically follows the gaze of the viewer’s pupil. Moreover, it mimics human vision by providing varying resolution across the FOV resulting in better utilization of the available space-bandwidth product of the SLM. We propose a system that can provide 28° × 28° instantaneous FOV within an extended FOV (the field of view that is covered by steering the instantaneous FOV in space) of 60° × 40° using a 4 K SLM, effectively providing a total enhancement of > 3 × in instantaneous FOV area, > 10 × in extended FOV area and the space-bandwidth product. We demonstrated 20° × 20° instantaneous FOV and 40° × 20° extended FOV in the experiments.”

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Publication: Scientific Reports
Issue/Year: Scientific Reports, Volume 10; Number 1; 2020
DOI: 10.1038/s41598-020-71986-9

Non-iterative phase hologram generation with optimized phase modulation

Author(s):

Lizhi Chen, Hao Zhang, Liangcai Cao and Guofan Jin

Abstract:

“A non-iterative algorithm is proposed to generate phase holograms with optimized phase modulation. A quadratic initial phase with continuous distributed spectrum is utilized to iteratively optimize the phase modulation in the reconstruction plane, which can be used as an optimized phase distribution for arbitrary target images. The phase hologram can be calculated directly according to the modulated wave field distribution in the reconstruction plane. Fast generation of the phase holograms can be achieved by this non-iterative implementation, and the avoidance of the random phase modulation helps to suppress the speckle noise. Numerical and
optical experiments have demonstrated that the proposed method can efficiently generate phase holograms with quality reconstructions.”

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Publication: Optics Express
Issue/Year: Vol. 28, Issue 8, pp. 11380-11392
DOI: 10.1364/OE.391518

High-Resolution Tunable Filter With Flexible Bandwidth and Power Attenuation Based on an LCoS Processor

Author(s):

Yunshu Gao, Genxiang Chen, Xiao Chen, Qian Zhang, Qiao Chen, Ce Zhang, Kai Tian, Zhongwei Tan and Chao Yu

Abstract:

“High-resolution optical filters and wavelength selective switches are the essential components in the current and next-generation dynamic optical networks. A high-resolution programmable filter for telecom application is proposed and experimentally demonstrated based on a 4 k phase-only liquid crystal on silicon (LCoS) spatial light modulator. The tuning resolution, bandwidth, and power attenuation for each wavelength channel can be modulated independently by remote software control. For each channel, the center wavelength is tuned in the step of 7.5 ± 1 pm and the 3 dB bandwidth achieves from 10 GHz to 3 THz. Furthermore, by multi-casting hologram design techniques for an LCoS, the power attenuation is adjusted from 0 dB to 30 dB with the step of 0.1 dB. The insertion loss is less than 6 dB across the entire C-band and 1.8 dB of it can be further improved by adopting an LCoS chip with smaller reflection loss. ”

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Publication: IEEE Photonics Journal
Issue/Year: Volume: 10 Issue: 6 (2018)
DOI: 10.1109/JPHOT.2018.2876347

On-Chip Detection of Orbital Angular Momentum Beam by Plasmonic Nanogratings

Author(s):

Ji Chen and Xi Chen and Tao Li and Shining Zhu

Abstract:

“Thanks to the unlimited orthogonal states, the orbital angular momentum (OAM) light is widely accepted as a promising carrier for high information multiplexing in optical communications, in which the OAM detection is an important issue. To keep up with the ever‐growing demand for compact integration, here, a plasmonic grating is employed to spatially couple the OAM modes into two separated propagating surface plasmon polariton (SPP) beams with different splitting angles. These splitting angles are found to strongly rely on the topological charges of the incident beams and are insensitive to the specific location of the OAM beam illumination, which provides an intuitive detection of the OAM modes without particular alignment. Besides, a further unidirectional SPP launching from the OAM beam is also achieved by a particular composite grating. With such composite grating, both the topological charge value and sign of OAM beam in a single measurement can be detected. Our results provide a convenient method for alignment‐free OAM detection by a compact device, and would inspire more multiplexing applications in nanophotonics.”

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Publication: Laser & Photonics Reviews
Issue/Year: Laser & Photonics Reviews Volume 12, Issue 8 (2018)
DOI: 10.1002/lpor.201700331

Non-iterative method for phase retrieval and coherence characterization by focus variation using a fixed star-shaped mask

Author(s):

A. P. Konijnenberg and Xingyuan Lu and Leixin Liu and W. M. J. Coene and Chengliang Zhao and H. P. Urbach

Abstract:

“A novel non-iterative phase retrieval method is proposed and demonstrated with a proof-of-principle experiment. The method uses a fixed specially designed mask and through-focus intensity measurements. It is demonstrated that this method is robust to spatial partial coherence in the illumination, making it suitable for coherent diffractive imaging using spatially partially coherent light, as well as for coherence characterization.”

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Publication: Optics Express
Issue/Year: Optics Express, Vol. 26, Issue 7, pp. 9332- 9343 (2018)
DOI: 10.1364/OE.26.009332