Optimal trap velocity in a dynamic holographic optical trap using a nematic liquid crystal spatial light modulator

A dynamic holographic optical trap uses a dynamic diffractive optical element such as a liquid crystal spatial light modulator to realize one or more optical traps with independent controls. Such holographic optical traps provide a number of flexibilities and conveniences useful in various applications. One key requirement for such a trap is the ability to move the trapped microscopic object from one point to the other with the optimal velocity. In this paper we develop a nematic liquid crystal spatial light modulator based holographic optical trap and experimentally investigate the optimal velocity feasible for trapped beads of different sizes, in such a trap. Our results show that the achievable velocity of the trapped bead is a function of size of the bead, step size, interval between two steps and power carried by the laser beam. We observe that the refresh rate of a nematic liquid crystal spatial light modulator is sufficient to achieve an optimal velocity approaching the theoretical limit in the respective holographic trap for beads with radius larger than the wavelength of light.

Experimental Study on Phase Conjecture Based on Two-dimensional Image and Carrying Three-dimensional Image With Mist in Electro-holographic Reconstruction *

A method is proposed for phase conjecture based on the intensity curve of a two-dimensional(2D) image by computing a polynomial equation. The intensity values of the 2D image, which represents the distance between the image detectors and the three-dimensional(3D) scene is converted to phase information by our method. The results of numerical calculation with phase conjecture are analyzed. And what’s more, the numerical reconstruction results with phase information obtained as initial phase factors of a complex object for Fresnel kinoform and dynamic pseudorandom-phase tomographic computer holography(DPP-TCH) are compared. The peak signal-to-noise ratio(PSNR) and correlation coefficient (CC) between the reconstructed images and original object are analyzed. An experimental system is designed for photoelectric holographic reconstruction based on phase-only liquid crystal spatial light modulator(LC-SLM) and mist screen. The electro-optical experimental results indicate that suppressed the speckle noise 3D images that can be observed with naked eye have been obtained.

Optical image encryption scheme with extended visual cryptography and non-mechanical ptychographic encoding

Non-mechanical ptychographic encoding (NPE) transforms the secret information into a series of diffractive patterns through a spatial light modulator, saving the need to fabricate the secret objects. Conventionally, the shares in extended visual cryptography (EVC) are printed on transparent sheets or fabricated with diffractive optical elements and metasurface, but these methods are expensive and disposable. To solve these problems, we proposed an optical image encryption scheme that combines EVC and NPE. In the encryption process, the secret image is decomposed into multiple shares that are digitally loaded on the spatial light modulator, and the ciphertexts are generated according to the ptychographic encoding scheme. The decryption is performed by superimposing the shares reconstructed from the ciphertexts. We present optical experiments to demonstrate the feasibility and effectiveness of the proposed method.

Optogenetic Manipulation of Cell Migration with High Spatiotemporal Resolution Using Lattice Lightsheet Microscopy

Lattice lightsheet microscopy (LLSM) is modified with the aim of manipulating cellular behavior with subcellular resolution through three-dimensional (3D) optogenetic activation. In this study, we report a straightforward implementation of the activation source in LLSM in which the stimulating light can be generated by changing the spatial light modulator (SLM) patterns and the annual masks. As a result, a Bessel beam as a stimulation source is integrated into the LLSM without changing the optical configuration, achieving high spatiotemporal activation. We show that the energy power required for optogenetic reactions is lower than 1 nW (24 mW/cm2) and membrane ruffling can be activated at different locations within a cell with subcellular resolution. We also demonstrate guided cell migration using optogenetic stimulation for up to 6 h with 463 volume imaging without noticeable damage to cells.

Adaptive Wave-Front Shaping and Beam Focusing through Fiber Bundles for High-Resolution Bioimaging

We demonstrate an adaptive wave-front shaping of optical beams transmitted through fiber bundles as a powerful resource for multisite, high-resolution bioimaging. With the phases of all the beamlets delivered through up to 6000 different fibers within the fiber bundle controlled individually, by means of a high-definition spatial light modulator, the overall beam transmitted through the fiber bundle can be focused into a beam waist with a diameter less than 1 μm within a targeted area in a biotissue, providing a diffraction-limited spatial resolution adequate for single-cell or even subcellular bioimaging. The field intensity in the adaptively-focused continuous-wave laser beam in our fiber-bundle-imaging setting is more than two orders of magnitude higher than the intensity of the speckle background. Once robust beam focusing was achieved with a suitable phase profile across the input face of the fiber bundle, the beam focus can be scanned over a targeted area with no need for a further adaptive search, by applying a physically intuitive, wave-front-tilting phase mask on the field of input beamlets. This method of beam-focus scanning promises imaging speeds compatible with the requirements of in vivo calcium imaging.

LCOS Spatial Light Modulator for Digital Holography

Liquid crystal on silicon (LCOS) spatial light modulator (SLM) is the most widely used optical engine for digital holography. This paper aims to provide an overview of the applications of phase-only LCOS in two-dimensional (2D) holography. It begins with a brief introduction to the holography theory along with its development trajectory, followed by the fundamental operating principle of phase-only LCOS SLMs. Hardware performance of LCOS SLMs (in terms of frame rate, phase linearity and flicker) and related experimental results are presented. Finally, potential improvements and applications are discussed for futuristic holographic displays. Full Text: PDF ReferencesM. Wolfke, Physikalische Zeitschrift 21, 495 (1920). DirectLink D. Gabor, "A New Microscopic Principle", Nature 161, 777 (1948). CrossRef H. Haken, "Laser Theory", Light and Matter 5, 14 (1970). CrossRef S. Benton, "Selected Papers on Three-dimensional displays", SPIE Press (2001). DirectLink X. Liang et al, "3D holographic display with optically addressed spatial light modulator", 3DTV-CON 2009 - 3rd 3DTV-Conference (2009). CrossRef J. Chen, W. Cranton, M. Fihn, "Handbook of Visual Display Technology", Springer (2012). CrossRef D. Rogers, "The chemistry of photography: From classical to digital technologies", Royal Society of Chemistry (2007). CrossRef S. Reichelt et al, "Depth cues in human visual perception and their realization in 3D displays", Proc. SPIE 7690, 76900B (2010). CrossRef A.W. Lohmann, D. Paris, "Binary Fraunhofer Holograms, Generated by Computer", Appl. Opt. 6, 1739 (1967). CrossRef J.W. Goodman, R.W. Lawrence, "Digital Image Formation from Electronically Detected Hologtrams", Appl. Phys. Lett 17, 77 (1967). CrossRef D.C. O'Brien, R.J. Mears, and W.A. Crossland, "Dynamic holographic interconnects that use ferroelectric liquid-crystal spatial light modulators", Appl. Opt. 33, 2795, (1994). CrossRef R.W. Gerchberg, and W.O. Saxton, "A practical algorithm for the determination of phase from image and diffraction plane pictures", Optik 35, 237 (1972). DirectLink M. Ernstoff, A. Leupp, M. Little, and H. Peterson, "Liquid crystal pictorial display", Proceedings of the 1973 International Electron Devices Meeting, IEEE, 548 (1973). CrossRef W.A. Crossland, P.J. Ayliffe, and P.W. Ross, "A dyed-phase-change liquid crystal display over a MOSFET switching array", Proc SID 23, 15 (1982). DirectLink M. Tang, and J. Wu, "Optical Correlation recoginition based on LCOS", Internation Symposium on Photoelectronic Detection and Imaging 2013, Optical Storage and Display Tech., 8913 (2013). CrossRef A. Hermerschmidt, et al. Holographic optical tweezers with real-time hologram calculation using a phase-only modulating LCOS-based SLM at 1064 nm, Complex Light and Optical Forces II, International Society for Optics and Photonics, 30282 (2008). CrossRef M. Wang, et al. "LCoS SLM Study and Its Application in Wavelength Selective Switch", Photonics 4, 22 (2017). CrossRef Z. Zhang, Z. You, and D. Chu, "Fundamentals of phase-only liquid crystal on silicon (LCOS) devices", Light Sci. & Appls. 3, e213 (2014). CrossRef D. Yang, and S. Wu, Fundamentals of liquid crystal devices, 2nd edition (Wiley 2015). CrossRef B. Prince, Semiconductor memories: A handbook of design, manufacture, and application, 2nd ed. (John Wiley & Sons 1996). DirectLink J.C. Jones, Liquid crystal displays, Handbook of optoelectronics: Enabling Technologies, 2nd ed. (CRC Press 2018). DirectLink A. Ayriyan, et al. "Simulation of the Static Electric Field Effect on the Director Orientation of Nematic Liquid Crystal in the Transition State", Phys. Wave Phenom. 27, 67 (2019). CrossRef S.M. Kelly, and M. O'Neil, Liquid crystal for electro-optic applications, Handbook of advanced electronics and photonic materials and devices 7, 15 (2000). DirectLink Y. Ji, et al., "Suspected Intraoperative Anaphylaxis to Gelatin Absorbable Hemostatic Sponge", J. SID 22, 4652 (2015). CrossRef X. Chang, Solution-processed ZnO nanoparticles for optically addressed spatial light modulator and other applications, Ph.D. thesis, (University of Cambridge, Cambridge 2019) CrossRef E. Moon, et al. "Holographic head-mounted display with RGB light emitting diode light source", Opt. Express 22, 6526 (2014). CrossRef G. Aad, et al. "Study of jet shapes in inclusive jet production in pp collisions at √s=7 TeV using the ATLAS detector", Phys Rev. D 83, 052003 (2011). CrossRef M. Pivnenko, K. Li, and D. Chu, "Sub-millisecond switching of multi-level liquid crystal on silicon spatial light modulators for increased information bandwidth", Opt. Express 29, 24614 (2021). CrossRef H. Yang, and D.P. Chu, "Phase flicker optimisation in digital liquid crystal on silicon devices", Opt. Express 27, 24556 (2019). CrossRef P. Bach-Y-Rita, et al. "Seeing with the Brain", Int. J. Hum. -Comput. Interact 15, 285 (2003). CrossRef Y. Tong, M. Pivnenko, and D. Chu, "Improvements of phase linearity and phase flicker of phase-only LCoS devices for holographic applications", Appl. Opt. 58, G248 (2019). CrossRef Y. Tong, M. Pivnenko, and D. Chu, "Implementation of 10-Bit Phase Modulation for Phase-Only LCOS Devices Using Deep Learning", Adv. Dev. & Instr. 1, 10 (2020). CrossRef H. Yang, and D. Chu, "Phase flicker optimisation in digital liquid crystal on silicon devices", Opt. Express 27, 24556 (2019). CrossRef J. García-Márquez, et al. "Mueller-Stokes characterization and optimization of a liquid crystal on silicon display showing depolarization", Opt.Express 16, 8431 (2008). CrossRef

Focal beam structuring by triple mixing of optical vortex lattices

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.