Showing papers on "Spatial light modulator published in 2015"
TL;DR: The results show that the proposed algorithm can perform quality reconstructions of 3D scenes with arbitrary depth information.
Abstract: We propose an algorithm based on fully computed holographic stereogram for calculating full-parallax computer-generated holograms (CGHs) with accurate depth cues. The proposed method integrates point source algorithm and holographic stereogram based algorithm to reconstruct the three-dimensional (3D) scenes. Precise accommodation cue and occlusion effect can be created, and computer graphics rendering techniques can be employed in the CGH generation to enhance the image fidelity. Optical experiments have been performed using a spatial light modulator (SLM) and a fabricated high-resolution hologram, the results show that our proposed algorithm can perform quality reconstructions of 3D scenes with arbitrary depth information.
135 citations
TL;DR: A combined imaging technique where confocal images are acquired through a multimode fiber by digitally engineering the excitation wavefront and then applying a virtual digital pinhole on the collected signal to acquire images through the fiber with significantly increased contrast.
Abstract: Acquiring high-contrast optical images deep inside biological tissues is still a challenging problem. Confocal microscopy is an important tool for biomedical imaging since it improves image quality by rejecting background signals. However, it suffers from low sensitivity in deep tissues due to light scattering. Recently, multimode fibers have provided a new paradigm for minimally invasive endoscopic imaging by controlling light propagation through them. Here we introduce a combined imaging technique where confocal images are acquired through a multimode fiber. We achieve this by digitally engineering the excitation wavefront and then applying a virtual digital pinhole on the collected signal. In this way, we are able to acquire images through the fiber with significantly increased contrast. With a fiber of numerical aperture 0.22, we achieve a lateral resolution of 1.5µm, and an axial resolution of 12.7µm. The point-scanning rate is currently limited by our spatial light modulator (20Hz).
132 citations
TL;DR: This work proposes and experimentally demonstrate the complete and simultaneous modulation of the amplitude, phase and arbitrary state of polarization of optical beams based on a 4-f system including a spatial light modulator (SLM).
Abstract: We propose and experimentally demonstrate the complete and simultaneous modulation of the amplitude, phase and arbitrary state of polarization of optical beams. Based on a 4-f system including a spatial light modulator (SLM), two orthogonally polarized beams serving as the base vector components are produced by a computer generated hologram. The complex amplitude of orthogonal components is realized by a macro-pixel encoding technique purposely designed for phase-only SLMs. Vector beams can be created from the coaxial superposition of the two base beams. This enables us to design optical fields with arbitrarily structured amplitude, phase and polarization by using only one SLM, and thus provides an easy-to-implement route for exploring the novel effects and expanding the functionality of vector beams with space-variant parameters.
100 citations
TL;DR: In this article, a high-resolution optically addressed spatial light modulator (OASLM) based on zinc oxide (ZnO) nanoparticles was presented, achieving a resolution of up to 825 lp mm−1 when operated at a voltage of below 6 V.
Abstract: Scientists in the UK have made a high-resolution optically addressed spatial light modulator (OASLM) based on zinc oxide (ZnO) nanoparticles. There is a strong demand for inexpensive OASLMs capable of producing high-resolution holograms over large active areas. The three researchers, who are all from the University of Cambridge, used a simple and inexpensive method to fabricate their OASLM — spin coating ZnO nanoparticles suspended in ethanol onto an indium–tin-oxide-coated glass substrate and then producing a photosensitive layer by low temperature (under 180 °C) annealing. The OASLM had a resolution of up to 825 lp mm−1 when operated at a voltage of below 6 V. The researchers attribute this performance to the use of a photoconductive film having a thin layer of semiconductor nanoparticles and a nematic liquid crystal with a relatively sharp threshold voltage.
94 citations
TL;DR: This work proposes a novel method for the generation of Airy vortex and Airy vector beams based on the modulation of dynamic and geometric phases that can be extended to generate any other types of optical beams with desirable phase and polarization.
Abstract: We propose a novel method for the generation of Airy vortex and Airy vector beams based on the modulation of dynamic and geometric phases. In our scheme, the Airy beam is generated by the dynamic phase with a spatial light modulator, and the vortex phase or the vector polarization is modulated by the geometric phase with a dielectric metasurface. The modulation of the geometric phase provides an extra degree of freedom to manipulate the phase and the polarization of Airy beams. This scheme can be extended to generate any other types of optical beams with desirable phase and polarization.
87 citations
TL;DR: In this paper, a multiple focal spot pattern (PP) was designed for parallel 2PP processing and the quantity and position of the multiple foci can be controlled by predesigned computer generated holograms (CGHs).
87 citations
20 Apr 2015
TL;DR: In this article, a combined system employing optical diffraction tomography and holographic optical tweezers is presented for simultaneous 3D visualization of the shapes and tracking positions of trapped microscopic samples.
Abstract: Precise tracking of three-dimensional (3D) positions of objects, often associated with optical tweezers, is important for the study of biophysics and cell biology. Although various approaches for 3D particle tracking have been proposed, most are limited in resolution and axial localization for objects of complex geometry. Holographic tomography systems circumvent these problems and offer improved capability in localization of objects over current methods. Here, we present a combined system employing optical diffraction tomography and holographic optical tweezers capable of simultaneous 3D visualization of the shapes and tracking positions of trapped microscopic samples. We demonstrated the capability of the present combined system using optically trapped silica beads and biological cells.
84 citations
TL;DR: In this article, a phase-only liquid-crystal spatial light modulator (SLM) was proposed to control both the phase and amplitude using a single SLM, thereby making the amplitude filters unnecessary.
Abstract: A technique is presented to produce any desired partially coherent Schell-model source using a single phase-only liquid-crystal spatial light modulator (SLM). Existing methods use SLMs in combination with amplitude filters to manipulate the phase and amplitude of an initially coherent source. The technique presented here controls both the phase and amplitude using a single SLM, thereby making the amplitude filters unnecessary. This simplifies the optical setup and significantly increases the utility and flexibility of the resulting system. The analytical development of the technique is presented and discussed. To validate the proposed approach, experimental results of three partially coherent Schell-model sources are presented and analyzed. A brief discussion of possible applications is provided in closing.
84 citations
TL;DR: In this article, the authors demonstrate an adaptive optical system based on nonlinear feedback from 3- and 4-photon fluorescence. The system is based on femtosecond pulses created by soliton self-frequency shift of a 1550-nm fiber-based femto-cond laser together with micro-electro-mechanical system (MEMS) phase spatial light modulator (SLM).
Abstract: We demonstrate adaptive optics system based on nonlinear feedback from 3- and 4-photon fluorescence. The system is based on femtosecond pulses created by soliton self-frequency shift of a 1550-nm fiber-based femtosecond laser together with micro-electro-mechanical system (MEMS) phase spatial light modulator (SLM). We perturb the 1020-segment SLM using an orthogonal Walsh sequence basis set with a modified version of three-point phase shifting interferometry. We show the improvement after aberrations correction in 3-photon signal from fluorescent beads. In addition, we compare the improvement obtained in the same adaptive optical system for 2-, 3- and 4-photon fluorescence using dye pool. We show that signal improvement resulting from aberration correction grows exponentially as a function of the order of nonlinearity.
71 citations
TL;DR: A high-power laser system with a high-quality near-field beam by using a liquid-crystal spatial light modulator (SLM) is demonstrated and an efficient spatial beam shaping algorithm is discussed which can improve the output nearfield beam quality effectively.
Abstract: We demonstrate a high-power laser system with a high-quality near-field beam by using a liquid-crystal spatial light modulator (SLM). An efficient spatial beam shaping algorithm is discussed which can improve the output nearfield beam quality effectively. Both small-signal and large-signal amplification situation of the laser are considered in the beam shaping algorithm. The experimental results show that the near field fluence modulation of output is improved from 1.99:1 to 1.26:1 by using the liquid-crystal SLM. Obvious uniform spatial fluence distribution and near-field beam quality improvement are observed.
71 citations
TL;DR: In this article, the authors experimentally measured the self-healing of the spatially inhomogeneous states of polarization of vector Bessel beams using a digital version of Durnin's method, using a spatial light modulator and a liquid crystal q-plate.
Abstract: We experimentally measured the self-healing of the spatially inhomogeneous states of polarization of vector Bessel beams. Radially and azimuthally polarized vector Bessel beams were experimentally generated via a digital version of Durnin's method, using a spatial light modulator in concert with a liquid crystal q-plate. As a proof of principle, their intensities and spatially inhomogeneous states of polarization were experimentally measured using Stokes polarimetry as they propagated through two disparate obstructions. It was found, similar to their intensities, that their spatially inhomogeneous states of polarization self-healed. The self-healing can be understood via geometric optics, i.e., the interference of the unobstructed conical rays in the shadow region of the obstruction, and may have applications in, for example, optical trapping.
TL;DR: In this paper, the application of evanescent photovoltaic (PV) fields, generated by visible illumination of Fe:LiNbO3 substrates, for parallel massive trapping and manipulation of micro- and nano-objects is critically reviewed.
Abstract: The application of evanescent photovoltaic (PV) fields, generated by visible illumination of Fe:LiNbO3 substrates, for parallel massive trapping and manipulation of micro- and nano-objects is critically reviewed. The technique has been often referred to as photovoltaic or photorefractive tweezers. The main advantage of the new method is that the involved electrophoretic and/or dielectrophoretic forces do not require any electrodes and large scale manipulation of nano-objects can be easily achieved using the patterning capabilities of light. The paper describes the experimental techniques for particle trapping and the main reported experimental results obtained with a variety of micro- and nano-particles (dielectric and conductive) and different illumination configurations (single beam, holographic geometry, and spatial light modulator projection). The report also pays attention to the physical basis of the method, namely, the coupling of the evanescent photorefractive fields to the dielectric response of the nano-particles. The role of a number of physical parameters such as the contrast and spatial periodicities of the illumination pattern or the particle deposition method is discussed. Moreover, the main properties of the obtained particle patterns in relation to potential applications are summarized, and first demonstrations reviewed. Finally, the PV method is discussed in comparison to other patterning strategies, such as those based on the pyroelectric response and the electric fields associated to domain poling of ferroelectric materials.
TL;DR: Spatial partitioning of the spatial light modulator is proposed to perform mosaic delivery of exposures at primary colors for seamless reconstruction of a white light viewable color hologram.
Abstract: The holographic wavefront printer decodes the wavefront coming from a three-dimensional object from a computer generated hologram displayed on a spatial light modulator. By recording this wavefront as an analog volume hologram this printing method is highly suitable for realistic color 3D imaging. We propose in the paper spatial partitioning of the spatial light modulator to perform mosaic delivery of exposures at primary colors for seamless reconstruction of a white light viewable color hologram. The method is verified for a 3 × 3 color partitioning scheme by a wavefront printer with demagnification of the light beam diffracted from the modulator.
TL;DR: A table screen 360-degree holographic display is proposed, with an increased screen size, having an expanded viewing zone over all horizontal directions around the table screen, and the viewing zones are localized to practically realize wavefront reconstruction.
Abstract: A table screen 360-degree holographic display is proposed, with an increased screen size, having an expanded viewing zone over all horizontal directions around the table screen. It consists of a microelectromechanical systems spatial light modulator (MEMS SLM), a magnifying imaging system, and a rotating screen. The MEMS SLM generates hologram patterns at a high frame rate, the magnifying imaging system increases the screen of the MEMS SLM, and the reduced viewing zones are scanned circularly by the rotating screen. The viewing zones are localized to practically realize wavefront reconstruction. An experimental system has been constructed. The generation of 360-degree three-dimensional (3D) images was achieved by scanning 800 reduced and localized viewing zones circularly. The table screen had a diameter of 100 mm, and the frame rate of 3D image generation was 28.4 Hz.
TL;DR: A method of increased acquisition speed on a two-beam SIM fluorescence microscope with a lateral resolution of ~100 nm at a maximum raw data acquisition rate of 162 frames per second (fps) with a region of interest of interest free of mechanically moving components is demonstrated.
Abstract: A significant improvement in acquisition speed of structured illumination microscopy (SIM) opens a new field of applications to this already well-established super-resolution method towards 3D scanning real-time imaging of living cells. We demonstrate a method of increased acquisition speed on a two-beam SIM fluorescence microscope with a lateral resolution of ~100 nm at a maximum raw data acquisition rate of 162 frames per second (fps) with a region of interest of 16.5 × 16.5 µm2, free of mechanically moving components. We use a programmable spatial light modulator (ferroelectric LCOS) which promises precise and rapid control of the excitation pattern in the sample plane. A passive Fourier filter and a segmented azimuthally patterned polarizer are used to perform structured illumination with maximum contrast. Furthermore, the free running mode in a modern sCMOS camera helps to achieve faster data acquisition.
TL;DR: A compressive snapshot color polarization imager that encodes spatial, spectral, and polarization information using a liquid crystal modulator is described and experimentally show that polarization imaging is compressible by multiplexing polarization states and the reconstruction results are presented.
Abstract: We describe a compressive snapshot color polarization imager that encodes spatial, spectral, and polarization information using a liquid crystal modulator. We experimentally show that polarization imaging is compressible by multiplexing polarization states and present the reconstruction results. This compressive camera captures the spatial distribution of four polarizations and three color channels. It achieves 30 PSNR.
TL;DR: An active, holographic tomography system, working with limited angle of projections, realized by optical-only, diffraction-based beam steering is demonstrated, providing an elegant solution to viewing angle shifting and adding new capabilities of the holographic microscope system.
Abstract: We demonstrate an active, holographic tomography system, working with limited angle of projections, realized by optical-only, diffraction-based beam steering. The system created for this purpose is a Mach–Zehnder interferometer modified to serve as a digital holographic microscope with a high numerical aperture illumination module and a spatial light modulator (SLM). Such a solution is fast and robust. Apart from providing an elegant solution to viewing angle shifting, it also adds new capabilities of the holographic microscope system. SLM, being an active optical element, allows wavefront correction in order to improve measurement accuracy. Integrated phase data captured with different illumination scenarios within a highly limited angular range are processed by a new tomographic reconstruction algorithm based on the compressed sensing technique: total variation minimization, which is applied here to reconstruct nonpiecewise constant samples. Finally, the accuracy of full measurement and the proposed processing path is tested for a calibrated three-dimensional micro-object as well as a biological object--C2C12 myoblast cell.
TL;DR: It is shown that the spatial profile of the pump field can be mapped onto the biphoton temporal wave function in the group delay regime and this spatial-to-temporal mapping enables the generation of narrow-band biphotons with controllable temporal waveforms.
Abstract: We demonstrate a technique for shaping the temporal wave function of biphotons generated from spatially modulated spontaneous four-wave mixing in cold atoms. We show that the spatial profile of the pump field can be mapped onto the biphoton temporal wave function in the group delay regime. The spatial profile of the pump laser beam is shaped by using a spatial light modulator. This spatial-to-temporal mapping enables the generation of narrow-band biphotons with controllable temporal waveforms.
TL;DR: This work demonstrates the photo-generation of THz linear antennas on a flat semiconductor layer by the structured optical illumination through a spatial light modulator, which opens a wide range of possibilities for the all-optical spatial control of resonances on surfaces and the concomitant control of Thz extinction and local fields.
Abstract: Electromagnetic resonances in conducting structures give rise to the enhancement of local fields and extinction efficiencies. Conducting structures are conventionally fabricated with a fixed geometry that determines their resonant response. Here, we challenge this conventional approach by demonstrating the photo-generation of THz linear antennas on a flat semiconductor layer by the structured optical illumination through a spatial light modulator. Free charge carriers are photo-excited only on selected areas, which enables the realization of different conducting antennas on the same sample by simply changing the illumination pattern, thus without the need of physically structuring the sample. These results open a wide range of possibilities for the all-optical spatial control of resonances on surfaces and the concomitant control of THz extinction and local fields.
Patent•
30 Apr 2015
TL;DR: In this article, a display includes a reflective spatial light modulator having a reflective surface, a lightguide comprising a core layer, a first cladding layer, and a light emitting region comprising a plurality of light extraction features arranged in a pattern that varies spatially in the light emitting regions to frustrate totally internally reflected light propagating within the core layer such that light exits from the core layers to the first claddings.
Abstract: A display includes a reflective spatial light modulator having a reflective surface, a lightguide comprising a core layer, a first cladding layer, and a light emitting region comprising a plurality of light extraction features arranged in a pattern that varies spatially in the light emitting region to frustrate totally internally reflected light propagating within the core layer such that light exits the core layer in the light emitting region into the first cladding layer. A light redirecting optical element is optically coupled to the second side of the first cladding layer, and includes a plurality of light redirecting features directing frustrated totally internally reflected light from the plurality of light extraction features toward the reflective spatial light modulator.
TL;DR: Active coherent beam combination using a 7-non-coupled core, polarization maintaining, air-clad, Yb-doped fiber is demonstrated as a monolithic and compact power-scaling concept for ultrafast fiber lasers.
Abstract: Active coherent beam combination using a 7-non-coupled core, polarization maintaining, air-clad, Yb-doped fiber is demonstrated as a monolithic and compact power-scaling concept for ultrafast fiber lasers. A microlens array matched to the multicore fiber and an active phase controller composed of a spatial light modulator applying a stochastic parallel gradient descent algorithm are utilized to perform coherent combining in the tiled aperture geometry. The mitigation of nonlinear effects at a pulse energy of 8.9 µJ and duration of 860 fs is experimentally verified at a repetition rate of 100 kHz. The experimental combining efficiency results in a far field central lobe carrying 49% of the total power, compared to an ideal value of 76%. This efficiency is primarily limited by group delay differences between cores which is identified as the main drawback of the system. Minimizing these group delay issues, e.g. by using short and straight rod-type multicore fibers, should allow a practical power scaling solution for femtosecond fiber systems.
TL;DR: The first realization of a wavelength-selective switch (WSS) with direct integration of few mode fibers (FMF) is fully described and the effect on data transmission of cascaded passband filtering and MDL build-up is experimentally investigated in detail.
Abstract: The first realization of a wavelength-selective switch (WSS) with direct integration of few mode fibers (FMF) is fully described. The free-space optics FMF-WSS dynamically steers spectral information-bearing beams containing three spatial modes from an input port to one of nine output ports using a phase spatial light modulator. Sources of mode dependent losses (MDL) are identified, analytically analyzed and experimentally confirmed on account of different modal sensitivities to fiber coupling in imperfect imaging and at spectral channel edges due to mode clipping. These performance impacting effects can be reduced by adhering to provided design guidelines, which scale in support of higher spatial mode counts. The effect on data transmission of cascaded passband filtering and MDL build-up is experimentally investigated in detail.
TL;DR: An iterative beam shaping algorithm to simultaneously shape the amplitude and phase of an optical beam is proposed, which is a phase-only distribution which can be conveniently realized with a spatial light modulator or a fabricated diffractive optical element.
Abstract: An iterative beam shaping algorithm is proposed to simultaneously shape the amplitude and phase of an optical beam. The proposed algorithm consists of one input plane and two completely overlapped output planes which refer to the output plane in real space. The two output planes are imposed with both amplitude and phase constraints, and the constrained areas in the two output planes are complementary. As a result, both the amplitude and phase in the entire output plane are controllable and arbitrary target complex amplitudes can be achieved with the proposed algorithm. The computing result of the proposed algorithm is a phase-only distribution which can be conveniently realized with a spatial light modulator or a fabricated diffractive optical element. Both simulations and experiments have verified the high performance of the proposed algorithm.
TL;DR: This work demonstrates the realization of a one-wave optical phase conjugation mirror using a spatial light modulator and demonstrates high throughput full-field light delivery through highly scattering biological tissue and multimode fibers, even for quantum dot fluorescence.
Abstract: Rewinding the arrow of time via phase conjugation is an intriguing phenomenon made possible by the wave property of light. Here, we demonstrate the realization of a one-wave optical phase conjugation mirror using a spatial light modulator. An adaptable single-mode filter is created, and a phase-conjugate beam is then prepared by reverse propagation through this filter. Our method is simple, alignment free, and fast while allowing high power throughput in the time-reversed wave, which has not been simultaneously demonstrated before. Using our method, we demonstrate high throughput full-field light delivery through highly scattering biological tissue and multimode fibers, even for quantum dot fluorescence.
Patent•
01 Apr 2015
TL;DR: In this article, a light source system and projection system was proposed, consisting of a first light source (1) producing first wide spectrum light, a second light source(2) producing second wavelength light, and a light splitting and light combining device (2) used to split and combine light.
Abstract: A light source system and projection system, the light source system comprising: a first light source ( 1 ) producing first wide spectrum light, a second light source ( 103 ) producing second wavelength light, a light splitting and light combining device ( 2 ) used to split and combine light, a first spatial light modulator ( 106 ), a second spatial light modulator ( 107 ), and a control device ( 108 ) controlling the first light source ( 1 ) and the second light source ( 103 ) and modulating the first spatial light modulator ( 106 ) and the second spatial light modulator ( 107 ). The projection system comprises the light source system. The light source system and projection system have high brightness and wide color gamut, effectively eliminating rainbow effect, and also have a simple structure and low cost.
TL;DR: The authors' experimental results show a trend that is in agreement with known theoretical expressions; however, the turbulence rescaling due to anisotropy shows some discrepancy with theory and requires more investigation.
Abstract: In this paper, we present a laboratory setup to simulate anisotropic, non-Kolmogorov turbulence. A sequence of numerical phase screens that incorporate the turbulence characteristics were applied to a spatial light modulator placed in the path of a laser beam with a Gaussian intensity profile and the resulting far-field intensity patterns were recorded by a CCD camera. The values of scintillation at the position of the maximum intensity were extracted from the images and compared with theoretical values. Our experimental results show a trend that is in agreement with known theoretical expressions; however, the turbulence rescaling due to anisotropy shows some discrepancy with theory and requires more investigation.
TL;DR: This work records a complex hologram of a real object using optical scanning holography, converts the complex form to binary data, and then reconstructs the recorded hologram using a spatial light modulator (SLM).
Abstract: In this paper, we present a three-dimensional holographic imaging system. The proposed approach records a complex hologram of a real object using optical scanning holography, converts the complex form to binary data, and then reconstructs the recorded hologram using a spatial light modulator (SLM). The conversion from the recorded hologram to a binary hologram is achieved using a direct binary search algorithm. We present experimental results that verify the efficacy of our approach. To the best of our knowledge, this is the first time that a hologram of a real object has been reconstructed using a binary SLM.
TL;DR: In this paper, the authors outline the steps necessary to create a laser with an intra-cavity spatial light modulator (SLM) for transverse mode control, and employ a commercial SLM as the back reflector in an otherwise conventional diode-pumped solid state laser.
Abstract: In this paper we outline the steps necessary to create a laser with an intra-cavity spatial light modulator (SLM) for transverse mode control. We employ a commercial SLM as the back reflector in an otherwise conventional diode-pumped solid state laser. We show that the geometry of the liquid crystal (LC) arrangement strongly influences the operating regime of the laser, from nominally amplitude-only mode control for twisted nematic LCs to nominally phase-only mode control for parallel-aligned LCs. We demonstrate both operating regimes experimentally and discuss the potential advantages of and improvements to this new technology.
TL;DR: A broadband terahertz (THz) spatial light modulator using 5×5 arrays of large area graphene supercapacitors using a passive matrix array of patterned graphene electrodes is demonstrated.
Abstract: In this Letter, we demonstrate a broadband terahertz (THz) spatial light modulator using 5×5 arrays of large area graphene supercapacitors. Our approach relies on controlling spatial charge distribution on a passive matrix array of patterned graphene electrodes. By changing the voltage bias applied to the rows and columns, we were able to pattern the THz transmittance through the device with high modulation depth and low operation voltage. We anticipate that the simplicity of the device architecture with high contrast THz modulation over a broad spectral range could provide new tools for THz imaging and communication systems.
TL;DR: In this article, a digital micro-mirror device (DMD) was used to generate high-speed Ince-Gaussian beam with high switching frequency of 5.2 kHz.
Abstract: Ince-Gaussian (IG) beam with elliptical profile, as a connection between Hermite-Gaussian (HG) and Laguerre-Gaussian (LG) beams, has showed unique advantages in some applications such as quantum entanglement and optical micromanipulation. However, its dynamic generation with high switching frequency is still challenging. Here, we experimentally reported the quick generation of Ince-Gaussian beam by using a digital micro-mirror device (DMD), which has the highest switching frequency of 5.2 kHz in principle. The configurable properties of DMD allow us to observe the quasi-smooth variation from LG (with ellipticity e=0) to IG and HG (e=∞) beam. This approach might pave a path to high-speed quantum communication in terms of IG beam. Additionally, the characterized axial plane intensity distribution exhibits a 3D mould potentially being employed for optical micromanipulation.