Azimuthal backflow in light carrying orbital angular momentum

Author(s):

Ghosh, Bohnishikha; Daniel, Anat; Gorzkowski, Bernard & Lapkiewicz, Radek

Abstract:

“M.V. Berry’s work [J. Phys. A: Math. Theor. 43, 415302 (2010)] highlighted the correspondence
between backflow in quantum mechanics and superoscillations in waves. Superoscillations refer to
situations where the local oscillation of a superposition is faster than its fastest Fourier component.
This concept has been used to demonstrate backflow in transverse linear momentum for optical
waves. In this work, we examine the interference of classical light carrying only negative orbital
angular momentum and observe in the dark fringes of such an interference, positive local orbital
angular momentum. This finding may have implications for the studies of light-matter interaction
and represents a step towards observing quantum backflow in two dimensions.”

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Publication: arXiv
Issue/Year: arXiv, 2023
arXiv: 10.48550/arXiv.2304.13124

Encrypting orbital angular momentum holography with ghost imaging

Author(s):

Ma, Junyao; Li, Zhe; Zhao, Shengmei & Wang, Le

Abstract:

“In this paper, we propose a multiple images simultaneous encryption scheme by encrypting the orbital angular momentum (OAM) holography with ghost imaging. By controlling the topological charge of the incident OAM light beam on the OAM-multiplexing hologram, different images can be selectively obtained for ghost imaging (GI). Followed by the random speckles illumination, the bucket detector values in GI are obtained and then considered as the ciphertext transmitted to the receiver. The authorized user can distill the correct relationship between the bucket detections and the illuminating speckle patterns with the key and the additional topological charges, so that each holographic image can be successfully recovered, while the eavesdropper can not obtain any information about the holographic image without the key. The eavesdropper even can not get clear holographic image when all the key is eavesdropped but without topological charges. The experimental results show that the proposed encryption scheme has a higher capacity for multiple images because there is no theoretical topological charge limit for the selectivity of OAM holography, and the results also show that the proposed encryption scheme is more secure and has a stronger robustness. Our method may provide a promising avenue for multi-image encryption and has the potential for more applications.”

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Publication: Opt. Express
Issue/Year: Opt. Express, Volume 31; Number 7; Pages 11717–11728; 2023
DOI: 10.1364/OE.483923

Focal beam structuring by triple mixing of optical vortex lattices

Author(s):

Stoyanov, Lyubomir; Maleshkov, Georgi; Stefanov, Ivan; Paulus, Gerhard G. & Dreischuh, Alexander

Abstract:

“On-demand generation and reshaping of arrays of focused laser beams is highly desired in many areas of science and technology. In this work, we present a versatile approach for laser beam structuring in the focal plane of a lens by triple mixing of square and/or hexagonal optical vortex lattices (OVLs). In the artificial far field the input Gaussian beam is reshaped into ordered arrays of bright beams with flat phase profiles. This is remarkable, since the bright focal peaks are surrounded by hundreds of OVs with their dark cores and two-dimensional phase dislocations. Numerical simulations and experimental evidences for this are shown, including a broad discussion of some of the possible scenarios for such mixing: triple mixing of square-shaped OVLs, triple mixing of hexagonal OVLs, as well as the two combined cases of mixing square-hexagonal-hexagonal and square-square-hexagonal OVLs. The particular ordering of the input phase distributions of the OV lattices on the used spatial light modulators is found to affect the orientation of the structures ruled by the hexagonal OVL. Reliable control parameters for the creation of the desired focal beam structures are the respective lattice node spacings. The presented approach is flexible, easily realizable by using a single spatial light modulator, and thus accessible in many laboratories.”

Link to Publications Page

Publication: Optical and Quantum Electronics
Issue/Year: Optical and Quantum Electronics, Volume 54; Number 1; 2021
DOI: 10.1007/s11082-021-03399-5

768-ary Laguerre-Gaussian-mode shift keying free-space optical communication based on convolutional neural networks

Author(s):

Luan, Haitao; Lin, Dajun; Li, Keyao; Meng, Weijia; Gu, Min & Fang, Xinyuan

Abstract:

“Beyond orbital angular momentum of Laguerre-Gaussian (LG) modes, the radial index can also be exploited as information channel in free-space optical (FSO) communication to extend the communication capacity, resulting in the LG- shift keying (LG-SK) FSO communications. However, the recognition of radial index is critical and tough when the superposed high-order LG modes are disturbed by the atmospheric turbulences (ATs). In this paper, the convolutional neural network (CNN) is utilized to recognize both the azimuthal and radial index of superposed LG modes. We experimentally demonstrate the application of CNN model in a 10-meter 768-ary LG-SK FSO communication system at the AT \(C^2_n= 10^{-14}m^{-\frac{2}{3}}\). Based on the high recognition accuracy of the CNN model (>95%) in the scheme, a colorful image can be transmitted and the peak signal-to-noise ratio of the received image can exceed 35 dB. We anticipate that our results can stimulate further researches on the utilization of the potential applications of LG modes with non-zero radial index based on the artificial-intelligence-enhanced optoelectronic systems.”

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Publication: Optics Express
Issue/Year: Optics Express, Volume 29; Number 13; Pages 19807; 2021
DOI: 10.1364/oe.420176

Reconfigurable generation of double-ring perfect vortex beam

Author(s):

Du, Yafei; Liu, Deming; Fu, Songnian; Wang, Yuncai & Qin, Yuwen

Abstract:

“Perfect vortex beam (PVB), whose ring radius is independent of its topological charge, play an important role in optical trapping and optical communication. Here, we experimentally demonstrate the reconfigurable double-ring PVB (DR-PVB) generation with independent manipulations of the amplitude, the radius, the width, and the topological charge for each ring. Based on complex amplitude modulation (CAM) with a phase-only spatial light modulator (SLM), we successfully verify the proposed DR-PVB generation scheme via the computer-generated hologram. Furthermore, we carry out a quantitative characterization for the generated DR-PVB, in terms of both the generation quality and the generation efficiency. The correlation coefficients of various reconfigurable DR-PVBs are above 0.8, together with the highest generation efficiency of 44%. We believe that, the proposed generation scheme of reconfigurable DR-PVB is desired for applications in both optical tweezers and orbital angular momentum (OAM) multiplexing.”

Link to Publications Page

Publication: Optics Express
Issue/Year: Optics Express, Volume 29; Number 11; Pages 17353; 2021
DOI: 10.1364/oe.424664

Time reversed optical waves by arbitrary vector spatiotemporal field generation

Author(s):

Mounaix, Mickael; Fontaine, Nicolas K.; Neilson, David T.; Ryf, Roland; Chen, Haoshuo; Alvarado-Zacarias, Juan Carlos & Carpenter, Joel

Abstract:

“Lossless linear wave propagation is symmetric in time, a principle which can be used to create time reversed waves. Such waves are special “pre-scattered” spatiotemporal fields, which propagate through a complex medium as if observing a scattering process in reverse, entering the medium as a complicated spatiotemporal field and arriving after propagation as a desired target field, such as a spatiotemporal focus. Time reversed waves have previously been demonstrated for relatively low frequency phenomena such as acoustics, water waves and microwaves. Many attempts have been made to extend these techniques into optics. However, the much higher frequencies of optics make for very different requirements. A fully time reversed wave is a volumetric field with arbitrary amplitude, phase and polarisation at every point in space and time. The creation of such fields has not previously been possible in optics. We demonstrate time reversed optical waves with a device capable of independently controlling all of light’s classical degrees of freedom simultaneously. Such a class of ultrafast wavefront shaper is capable of generating a sequence of arbitrary 2D spatial/polarisation wavefronts at a bandwidth limited rate of 4.4 THz. This ability to manipulate the full field of an optical beam could be used to control both linear and nonlinear optical phenomena.”

Link to Publications Page

Publication: Nature Communications
Issue/Year: Nature Communications, Volume 11; Number 1; 2020
DOI: 10.1038/s41467-020-19601-3

Hologram generation via Hilbert transform

Author(s):

Tomoyoshi Shimobaba, Takashi Kakue, Yota Yamamoto, Ikuo Hoshi, Harutaka Shiomi, Takashi Nishitsuji, Naoki Takada, and Tomoyoshi Ito

Abstract:

“We propose an indirect method for generating a complex hologram and phase-only hologram from an amplitude hologram using the Hilbert transform. The Hilbert transform generates an imaginary part of complex amplitude from only an amplitude hologram, resulting in the reduction of the total computational complexity of complex and phase-only holograms. More importantly, the proposed method can reduce the hardware resources of dedicated hologram processors.”

Link to Publications Page

Publication: OSA Continuum
Issue/Year: Vol. 3, Issue 6, pp. 1498-1503 (2020)
DOI: 10.1364/OSAC.395003

Polarization nano-tomography of tightly focused light landscapes by self-assembled monolayers

Author(s):

Eileen Otte, Kemal Tekce, Sebastian Lamping, Bart Jan Ravoo and Cornelia Denz
Abstract:

“Recently, four-dimensional (4D) functional nano-materials have attracted considerable attention due to their impact in cutting-edge fields such as nano-(opto)electronics, -biotechnology or -biomedicine. Prominent optical functionalizations, representing the fourth dimension, require precisely tailored light fields for its optimal implementation. These fields need to be like-wise 4D, i.e., nano-structured in three-dimensional (3D) space while polarization embeds additional longitudinal components. Though a couple of approaches to realize 4D fields have been suggested, their breakthrough is impeded by a lack of appropriate analysis techniques. Combining molecular self-assembly, i.e., nano-chemistry, and nano-optics, we propose a polarization nano-tomography of respective fields using the functional material itself as a sensor. Our method allows a single-shot identification of non-paraxial light fields at nano-scale resolution without any data post-processing. We prove its functionality numerically and experimentally, elucidating its amplitude, phase and 3D polarization sensitivity. We analyze non-paraxial field properties, demonstrating our method’s capability and potential for next generation 4D materials.”

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Publication: Nature Communications
Issue/Year: Nature Communications volume 10, Article number: 4308 (2019)
DOI: 10.1038/s41467-019-12127-3

A full-color compact 3D see-through near-eye display system based on complex amplitude modulation

Author(s):

Zhang, Zhiqi; Liu, Juan; Gao, Qiankun; Duan, Xinhui & Shi, Xueliang

Abstract:

“For complex amplitude modulation (CAM)-based three-dimensional (3D) near-eye systems, it is a challenge to realize colorful 3D display by using spatial light modulator (SLM) and grating. Here, a full-color compact 3D see-through near-eye display (NED) system by CAM is proposed. Computer generated holograms (CGHs) for different wavelengths are calculated separately. Each CGH contains two position-shifted sub-holograms and the separated distance is carefully calibrated to eliminate chromatic aberration. Colorful 3D images are synthesized through time-multiplexing. Color managements are performed and chromatic aberration of the system is analyzed to provide better colorful effect. The system structure is integrated to be compact and a prototype is implemented. Pre-compensation is added on CGHs to offset the system’s assembling errors. Optical experiment results show that the proposed system can provide good 3D full-color see-through performance without vergence-accommodation conflict (VAC). Dynamic colorful display ability is also tested, which shows good potential for interactive NED in the future.”

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Publication: Optics Express
Issue/Year: Optics Express, Volume 27; Number 5; Pages 7023; 2019
DOI: 10.1364/oe.27.007023

Three-dimensional vectorial multifocal arrays created by pseudo-period encoding

Author(s):

Tingting Zeng and Chenliang Chang and Zhaozhong Chen and Hui-Tian Wang and Jianping Ding

Abstract:

“Multifocal arrays have been attracting considerable attention recently owing to their potential applications in parallel optical tweezers, parallel single-molecule orientation determination, parallel recording and multifocal multiphoton microscopy. However, the generation of vectorial multifocal arrays with a tailorable structure and polarization state remains a great challenge, and reports on multifocal arrays have hitherto been restricted either to scalar focal spots without polarization versatility or to regular arrays with fixed spacing. In this work, we propose a specific pseudo-period encoding technique to create three-dimensional (3D) vectorial multifocal arrays with the ability to manipulate the position, polarization state and intensity of each focal spot. We experimentally validated the flexibility of our approach in the generation of 3D vectorial multiple spots with polarization multiplicity and position tunability.”

Link to Publications Page

Publication: Journal of Optics
Issue/Year: Journal of Optics, Volume 20, Number 6
DOI: 10.1088/2040-8986/aac1de