Manipulating aqueous droplets by light-induced virtual electrodes

Author(s):

Zamboni, Riccardo; Imbrock, Jörg & Denz, Cornelia

Abstract:

“The precise spatio-temporal manipulation of droplets is fundamental for many lab-on-a-chip systems with applications in biology, healthcare and chemistry. Different approaches have been investigated, including thermal, chemical and electrical methodologies. Among this latter, electrophoresis (EP) and dielectrophoresis (DEP) play a key role, since they are highly compatible with microfluidic systems and provide sufficiently strong forces to control up to microliter volume aqueous droplets. However, EP and DEP techniques typically require the presence of metallic electrodes to create the desired electric fields, making these approaches less flexible and efficient than those exploiting pure optical techniques. Iron-doped lithium niobate (LiNbO3:Fe) allows for the generation of strong electric field modulation due to an inhomogenous illumination, thanks to its photovoltaic properties. These photoinduced fields interact as EP and DEP forces with microdroplets, while guaranteeing the flexibility provided by optical field-based modulation. Indeed, the combination with well-known techniques to control and modulate light fields can be exploited to generate virtual electrodes on the material, achieving reliable as well as flexible devices for water droplets control. In our approach, the photoinduced fields generated by the complex illumination of LiNbO3:Fe are exploited to control motion and trajectory of water droplets inside microfluidic channel. Moreover, the crystal is integrated in standard droplet microfluidic polymeric device, substituting the usual glass substrate and, thus without hindering the portability. This feature combined with the control of positions of aqueous droplets represents a key tool for several applications of customized lab-on-a-chip systems, highlighting the capabilities of LinbO3:Fe-based virtual electrodes.”

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Publication: SPIE Proceedings
Issue/Year: Proc. SPIE 11798, Optical Trapping and Optical Micromanipulation XVIII, 1179824, 2021
DOI: 10.1117/12.2594165

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

Quantum cryptography technique: A way to improve security challenges in mobile cloud computing (MCC)

Author(s):

Abidin, Shafiqul; Swami, Amit; Ramirez-As{‘{i}}s, Edwin; Alvarado-Tolentino, Joseph; Maurya, Rajesh Kumar & Hussain, Naziya

Abstract:

“Quantum cryptography concentrates on the solution of cryptography that is imperishable due to the reason of fortification of secrecy which is applied to the public key distribution of quantum. It is a very prominent technology in which 2 beings can securely communicate along with the sights belongings to quantum physics. However, on basis of classical level cryptography, the used encodes were bits for data. As quantum utilizes the photons or particles polarize ones for encoding the quantized property. This is presented in qubits as a unit. Transmissions depend directly on the inalienable mechanic’s law of quantum for security. This paper includes detailed insight into the three most used and appreciated quantum cryptography applications that are providing its domain-wide service in the field of mobile cloud computing. These services are (it) DARPA Network, (ii) IPSEC implementation, and (iii) the twisted light HD implementation along with quantum elements, key distribution, and protocols.”

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Publication: Materials Today: Proceedings
Issue/Year: Materials Today: Proceedings, 2021
DOI: 10.1016/j.matpr.2021.05.593

Holographic near-eye display based on complex amplitude modulation with band-limited zone plates

Author(s):

Chen, Yun; Hua, Minjie; Zhang, Tianshun; Zhou, Mingxin; Wu, Jianhong & Zou, Wenlong

Abstract:

“A holographic near-eye display (NED) system based on complex amplitude modulation (CAM) with band-limited zone plates is proposed. The whole system mainly consists of a phase-only spatial light modulator (SLM), an Abbe-Porter filter system, an eyepiece, and an image combiner. The point source method based on band limited zone plates is used to accurately control the bandwidth of the target complex amplitude. The effects of intensity modulation coefficient γ in the frequency-filtering method on the intensity and the quality of reconstructed images are analyzed, which provide a judgment basis for selecting the appropriate value of γ. We also derive the expressions of the field of view (FOV) and exit pupil of the NED system. Since the holographic image is magnified in two steps in this system, the large FOV can be obtained. The optical experimental results show that the proposed system can provide a dynamic holographic three-dimensional (3D) augmented reality (AR) display with a 23.5°horizontal FOV.”

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Publication: Optics Express
Issue/Year: Optics Express, Volume 29; Number 14; Pages 22749; 2021
DOI: 10.1364/oe.431032

Single-plane and multiplane quantitative phase imaging by self-reference on-axis holography with a phase-shifting method

Author(s):

Hai, Nathaniel & Rosen, Joseph

Abstract:

“A new quantitative phase imaging approach is proposed based on self-reference holography. Three on-axis interferograms with different values of the phase filter are superposed. The superposition yields a more accurate phase map of the wavefront emerging from the object, compared with standard off-axis interferometry. Reduced temporal noise levels in the measured phase map and efficient phase recovery process for optically thin and thick transmissive phase objects highlight the applicability of the suggested framework for various fields ranging from metrology to bio-imaging. Qualitative phase imaging is also done online without altering the optical configuration. Qualitative phase detections of multiple planes of interest are converted to quantitative phase maps of the multiplane scene by a rapid phase contrast-based phase retrieval algorithm, from a single camera exposure and with no moving parts in the system.”

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Publication: Optics Express
Issue/Year: Optics Express, Volume 29; Number 15; Pages 24210; 2021
DOI: 10.1364/oe.431529

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

Control of femtosecond single-filament formation via feedback-based wavefront shaping

Author(s):

Li, Jing; Tan, Wenjiang; Si, Jinhai; Tang, Shiyun; Kang, Zhen & Hou, Xun

Abstract:

“We demonstrate the control of femtosecond single-filament formation via feedback-based wavefront shaping. It is observed that the optimal phase profile forms a single-filament with closed-loop genetic algorithm. Using this method, the position stability of the filament can be significantly improved, and the position of the single filament can be flexibly adjusted. Additionally, a two-step approach combining the premodulation of pinhole with wavefront shaping is presented for forming a bright single filament rapidly.”

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Publication: Optics Communications
Issue/Year: Optics Communications, Volume 490; Pages 126929; 2021
DOI: 10.1016/j.optcom.2021.126929

Toward simple, generalizable neural networks with universal training for low-SWaP hybrid vision

Author(s):

Muminov, Baurzhan; Perry, Altai; Hyder, Rakib; Asif, M. Salman & Vuong, Luat T.

Abstract:

“Speed, generalizability, and robustness are fundamental issues for building lightweight computational cameras. Here we demonstrate generalizable image reconstruction with the simplest of hybrid machine vision systems: linear optical preprocessors combined with no-hidden-layer, “small-brain” neural networks. Surprisingly, such simple neural networks are capable of learning the image reconstruction from a range of coded diffraction patterns using two masks. We investigate the possibility of generalized or “universal training” with these small brains. Neural networks trained with sinusoidal or random patterns uniformly distribute errors around a reconstructed image, whereas models trained with a combination of sharp and curved shapes (the phase pattern of optical vortices) reconstruct edges more boldly. We illustrate variable convergence of these simple neural networks and relate learnability of an image to its singular value decomposition entropy of the image. We also provide heuristic experimental results. With thresholding, we achieve robust reconstruction of various disjoint datasets. Our work is favorable for future real-time low size, weight, and power hybrid vision: we reconstruct images on a 15 W laptop CPU with 15,000 frames per second: faster by a factor of 3 than previously reported results and 3 orders of magnitude faster than convolutional neural networks.”

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Publication: Photonics Research
Issue/Year: Photonics Research, Volume 9; Number 7; Pages B253; 2021
DOI: 10.1364/prj.416614

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.”

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

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