Spatial Light Modulator Technology Research Articles

Enhanced coupling between ballistic exciton-polariton condensates through tailored pumping

We propose a method to enhance the spatial coupling between ballistic exciton-polariton condensates in a semiconductor microcavity based on available spatial light modulator technologies. Our method, verified by numerically solving a generalized Gross-Pitaevskii model, exploits the strong nonequilibrium nature of exciton-polariton condensation driven by localized nonresonant optical excitation. Tailoring the excitation beam profile from a Gaussian into a polygonal shape results in refracted and focused radial streams of outflowing polaritons from the excited condensate which can be directed towards nearest neighbors. Our method can be used to lower the threshold power needed to achieve polariton condensation and increase spatial coherence in extended systems, paving the way towards creating extremely large-scale quantum fluids of light.

Active focal-plane coronagraphy with liquid-crystal spatial-light modulators: broadband contrast performance in the visible.

The technological progress in spatial-light modulator (SLM) technology has made it possible to use those devices as programmable active focal-plane phase coronagraphic masks, opening the door to novel versatile and adaptive high-contrast imaging observation strategies. However, the scalar nature of the SLM-induced phase response is a potential hurdle when applying the approach to wideband light, as is typical in astronomical imaging. For the first time, to our knowledge, we present laboratory results with broadband light (up to ∼12% bandwidth) for two commercially available SLM devices used as active focal-plane phase masks in the visible regime (640 nm). It is shown that under ideal or realistic telescope aperture conditions, the contrast performance is negligibly affected in this bandwidth regime, reaching a sufficient level for ground-based high-contrast imaging, which is typically dominated by atmospheric residuals.

57‐1: ActiveHogel Light‐field Display: An Application of Next Generation μLED Pixels

Light‐field displays produce full‐parallax/perspective correct 3D aerial imagery for one or more simultaneous viewers. While there have been a few prototype, large‐format light‐field displays demonstrated using OLED, LCD, LCoS or other spatial light modulator (SLM) technology, they suffered from projection artifacts that degraded the visualization experience. These artifacts can be resolved by developing a custom μLED SLM specially designed for light‐field displays. FoVI3D's ActiveHogel Module and Tile presented in this paper highlight the architecture and benefits of a μLED light‐field display.

Reconfigurable terahertz metasurfaces coherently controlled by wavelength-scale-structured light.

Structuring light–matter interaction at a deeply subwavelength scale is fundamental to optical metamaterials and metasurfaces. Conventionally, the operation of a metasurface is determined by the collective electric polarization response of its lithographically defined structures. The inseparability of electric polarization and current density provides the opportunity to construct metasurfaces from current elements instead of nanostructures. Here, we realize metasurfaces using structured light rather than structured materials. Using coherent control, we transfer structure from light to transient currents in a semiconductor, which act as a source for terahertz radiation. A spatial light modulator is used to control the spatial structure of the currents and the resulting terahertz radiation with a resolution of , or approximately at a frequency of 1 THz. The independence of the currents from any predefined structures and the maturity of spatial light modulator technology enable this metasurface to be reconfigured with unprecedented flexibility.

Wide-viewing full-color depthmap computer-generated holograms.

An efficient synthesis algorithm for wide-viewing full-color depthmap computer-generated holograms is proposed. We develop a precise computational algorithm integrating wave-optic geometry-mapping, color-matching, and noise-filtering to multiplex multiview elementary computer-generated holograms (CGHs) into a single high-definition CGH without three-dimensional perspective distortion or color dispersion. Computational parallelism is exploited to achieve significant computational efficiency improvement in the production throughput of full-color wide-viewing angle CGHs. The proposed algorithm is verified through the full-color binary hologram reconstruction experiments utilizing an off-axis R·G·B simultaneous illumination method, which suggests the feasibility of the full-color sub-wavelength binary spatial light modulator technology.

单像素成像在特殊波段及三维成像的应用发展

Different from traditional array-detector imaging technology, single pixel imaging(SPI) technology, which is considered as a novel computational imaging technology, uses a bucket detector with no spatial resolution capability and combines with the spatial light field modulation technology to reconstruct the intensity of the object by correlation algorithm, which has received extensive attention. In recent years, SPI has been widely used with different light source, especially in some special wavebands, where the array-detectors are expensive or even impossible to be made. SPI has gradually developed into an alternative technology with low cost and high quality. In addition, a large number of works of SPI have been proposed in 3D imaging technology. The basic principle and application development of single pixel imaging was introduced. Its application in fringe projection 3D imaging was also introduced emphatically.

Full-color computational holographic near-eye display

ABSTRACTNear-eye displays (NEDs) are an excellent candidate for the future of augmented reality. Conventional micro-display based NED designs mostly provide stereoscopic 3D experience, which leads to visual discomfort due to vergence-accommodation conflict. Computational holographic near-eye displays (HNEDs) can simultaneously provide wide FOV, retinal resolution, attractive form-factor, and natural depth cues including accommodation. In HNEDs, computer-generated holograms (CGHs) are displayed on a spatial light modulators (SLMs). We propose a CGH computation algorithm that applies to arbitrary paraxial optical architectures; where the SLM illumination beam can be collimated, converging or diverging, and the SLM image as seen by the eye box plane may form at an arbitrary location, and can be virtual or real. Our CGH computation procedure eliminates speckle noise, which is observed in all other laser-based displays, and chromatic aberrations resulting from the light sources and the optics. Our proof-of-concept experiments demonstrate that HNEDs with simple optical architectures can deliver natural 3D images within a wide FOV (70 degrees) at retinal resolution (30 cycles-per-degree), exceeding 4000 resolvable pixels on a line using a printed binary mask. With the advances in SLM technology, HNEDs can realize the ultimate personalized display, meeting the demand of emerging augmented and virtual reality applications.

Visual simulators replicate vision with multifocal lenses

Adaptive optics (AO) visual simulators based on deformable mirrors, spatial light modulators or optotunable lenses are increasingly used to simulate vision through different multifocal lens designs. However, the correspondence of this simulation with that obtained through real intraocular lenses (IOLs) tested on the same eyes has not been, to our knowledge, demonstrated. We compare through-focus (TF) optical and visual quality produced by real multifocal IOLs (M-IOLs) -bifocal refractive and trifocal diffractive- projected on the subiect’s eye with those same designs simulated with a spatial light modulator (SLM) or an optotunable lens working in temporal multiplexing mode (SimVis technology). Measurements were performed on 7 cyclopleged subjects using a custom-made multichannel 3-active-optical-elements polychromatic AO Visual Simulator in monochromatic light. The same system was used to demonstrate performance of the real IOLs, SLM and SimVis technology simulations on bench using double-pass imaging on an artificial eye. Results show a general good correspondence between the TF performance with the real and simulated M-IOLs, both optically (on bench) and visually (measured visual acuity in patients). We demonstrate that visual simulations in an AO environment capture to a large extent the individual optical and visual performance obtained with real M-IOLs, both in absolute values and in the shape of through-focus curves.

Q&A with Jasper Display Corp.

Jasper Display Corp. is a leading designer of spatial light modulators (SLMs) and micro‐displays for both LCOS and microLEDs. In 2017, Jasper and partner glω received an I‐Zone Best Prototype Honorable Mention from SID for their megapixel silicon backplane (4K × 2K) and spatial light modulator technology for microdisplays. Information Display recently had the chance to speak with Jasper's vice president of marketing and engineering, Mike Stover.

Investigation of the thermal and optical performance of a spatial light modulator with high average power picosecond laser exposure for materials processing applications

Spatial light modulators (SLMs) addressed with computer generated holograms (CGHs) can create structured light fields on demand when an incident laser beam is diffracted by a phase CGH. The power handling limitations of these devices based on a liquid crystal layer has always been of some concern. With careful engineering of chip thermal management, we report the detailed optical phase and temperature response of a liquid cooled SLM exposed to picosecond laser powers up to 〈P〉 = 220 W at 1064 nm. This information is critical for determining device performance at high laser powers. SLM chip temperature rose linearly with incident laser exposure, increasing by only 5 °C at 〈P〉 = 220 W incident power, measured with a thermal imaging camera. Thermal response time with continuous exposure was 1–2 s. The optical phase response with incident power approaches 2π radians with average power up to 〈P〉 = 130 W, hence the operational limit, while above this power, liquid crystal thickness variations limit phase response to just over radians. Modelling of the thermal and phase response with exposure is also presented, supporting experimental observations well. These remarkable performance characteristics show that liquid crystal based SLM technology is highly robust when efficiently cooled. High speed, multi-beam plasmonic surface micro-structuring at a rate R = 8 cm2 s−1 is achieved on polished metal surfaces at 〈P〉 = 25 W exposure while diffractive, multi-beam surface ablation with average power 〈P〉 =100 W on stainless steel is demonstrated with ablation rate of ~4 mm3 min−1. However, above 130 W, first order diffraction efficiency drops significantly in accord with the observed operational limit. Continuous exposure for a period of 45 min at a laser power of 〈P〉 = 160 W did not result in any detectable drop in diffraction efficiency, confirmed afterwards by the efficient parallel beam processing at 〈P〉 = 100 W. Hence, no permanent changes in SLM phase response characteristics have been detected. This research work will help to accelerate the use of liquid crystal spatial light modulators for both scientific and ultra high throughput laser-materials micro-structuring applications.

Thermal and optical performance characteristics of a spatial light modulator with high average power picosecond laser exposure applied to materials processing applications

A spatial light modulator (SLM) addressed with Computer Generated Holograms (CGH’s) can create structured light fields when an incident laser beam is diffracted by a phase CGH. The power handling limitations of SLMs based on a liquid crystal layer have always been of some concern. Now, with careful engineering of chip thermal management, we present the detailed optical phase and temperature response of a liquid cooled SLM exposed to picosecond laser average powers up to 220W at 1064nm – new knowledge critical for determining device performance at high laser powers. SLM chip temperature rose linearly with incident laser exposure, increasing by only 5°C at 220W incident power, measured with a thermal imaging camera. Thermal response time with continuous exposure was 1-2 seconds. The optical phase response with incident power approaches 2π radians with average powers up to 130W while above this power, liquid crystal thickness variations limit phase response to just over π radians. These remarkable performance characteristics show that liquid crystal based SLM technology is highly robust when efficiently cooled. High speed, multi-beam plasmonic surface micro-structuring at a coverage rate of 8cm2s-1 is achieved on polished metal surfaces at 25W exposure, while diffractive multi-beam surface ablation on stainless steel at an ablation rate of ∼4mm3min-1 is demonstrated with average power 100W. Continuous exposure for many hours exceeding 100W laser power did not result in any detectable drop in diffraction efficiency hence no permanent changes in SLM phase response characteristics have been observed This research work will help to accelerate the use of liquid crystal SLMs for both scientific and ultra-high throughput laser-materials micro-structuring applications.

Enabling the study of photons orbital angular momentum for optical communications

The internet data traffic capacity is reaching the limits imposed by optical fiber nonlinear effects, having almost exhausted the available degrees of freedom needed to orthogonally multiplex data. Therefore, new methods should be developed to avoid the capacity crunch. The orbital angular momentum (OAM) of photons may be used as an additional degree of freedom. In this article, in order to enable the study of applications of OAM for optical communications, an experimental setup for modulation and demodulation of free space OAM carrying beams was conceived based on twsited nematic spatial light modulator technology. This work assesses the viability of this technology pointing that this low cost solution can enable the application of OAM for optical communications.

Light-induced self-assembly of active rectification devices.

Self-propelled colloidal objects, such as motile bacteria or synthetic microswimmers, have microscopically irreversible individual dynamics-a feature they share with all living systems. The incoherent behavior of individual swimmers can be harnessed (or "rectified") by microfluidic devices that create systematic motions that are impossible in equilibrium. We present a computational proof-of-concept study showing that such active rectification devices could be created directly from an unstructured "primordial soup" of light-controlled motile particles, solely by using spatially modulated illumination to control their local propulsion speed. Alongside both microscopic irreversibility and speed modulation, our mechanism requires spatial symmetry breaking, such as a chevron light pattern, and strong interactions between particles, such as volume exclusion, which cause a collisional slowdown at high density. Together, we show how these four factors create a novel, many-body rectification mechanism. Our work suggests that standard spatial light modulator technology might allow the programmable, light-induced self-assembly of active rectification devices from an unstructured particle bath.

Fairy Lights in Femtoseconds

We present a method of rendering aerial and volumetric graphics using femtosecond lasers. A high-intensity laser excites physical matter to emit light at an arbitrary three-dimensional position. Popular applications can thus be explored, especially because plasma induced by a femtosecond laser is less harmful than that generated by a nanosecond laser. There are two methods of rendering graphics with a femtosecond laser in air: producing holograms using spatial light modulation technology and scanning of a laser beam by a galvano mirror. The holograms and workspace of the system proposed here occupy a volume of up to 1 cm 3 ; however, this size is scalable depending on the optical devices and their setup. This article provides details of the principles, system setup, and experimental evaluation, and discusses the scalability, design space, and applications of this system. We tested two laser sources: an adjustable (30--100fs) laser that projects up to 1,000 pulses/s at an energy of up to 7mJ/pulse and a 269fs laser that projects up to 200,000 pulses/s at an energy of up to 50μJ/pulse. We confirmed that the spatiotemporal resolution of volumetric displays implemented using these laser sources is 4,000 and 200,000 dots/s, respectively. Although we focus on laser-induced plasma in air, the discussion presented here is also applicable to other rendering principles such as fluorescence and microbubbles in solid or liquid materials.

Phase modulation using different orientations of a chiral nematic in liquid crystal over silicon devices

ABSTRACTModulation of the intensity of light by high quality reflective micro-displays is predominantly carried out by liquid crystal over silicon (LCoS) spatial light modulator (SLM) technology for applications such as pico-projectors. Wider use of these devices, in applications such as computer-generated holography and optical correlation, is limited by their phase modulation ability and illumination polarisation state dependence. These devices rely on planar or twisted nematic liquid crystals to modulate the light, but due to their viscoelastic properties they are inherently slow. Research into the use of the polymer stabilised blue phase has already shown that it can offer high speed phase modulation. However, other chiral nematic orientations are yet to be compared in LCoS devices. In this article, we demonstrate that polymer-stabilised chiral nematic liquid crystal electro-optical effects can offer phase modulation in silicon backplane devices. The uniform standing helix and focal conic textures are shown to be independent of the input light polarisation state and the uniform lying helix is shown to be polarisation dependent. These optical responses are then compared with that of the blue phase to identify a suitable orientation for further development in LCoS technology in order to find a high-speed, full phase modulating material.

Polarization-independent phase modulation using a blue-phase liquid crystal over silicon device.

Liquid crystal over silicon (LCoS) spatial light modulator technology has become dominant in industries such as pico-projection, which require high-quality reflective microdisplays for intensity modulation of light. They are, however, restricted from being used in wider optical applications, such as computer-generated holography, adaptive optics, and optical correlation, due to their phase modulation ability. The main drawback of these devices is that their modulation is based on simple planar or twisted nematic liquid crystals, which are inherently slow mechanisms due to their viscoelastic properties. Their use is also limited due to fact that the phase modulation is dependent on the state of polarization of the illumination. In this paper, we demonstrate that a polymer-stabilized blue-phase liquid crystal can offer both phase modulation and high speed switching in a silicon backplane device which is independent of the input polarization state. The LCoS device shows continuous phase modulation of light with a submillisecond switching time and insensitivity to the input light polarization direction. This type of phase modulation opens up a whole new class of applications for LCoS technology.

Demonstration of Multi-Casting in a 1 × 9 LCOS Wavelength Selective Switch

A multi-functional 1 × 9 wavelength selective switch based on liquid crystal on silicon (LCOS) spatial light modulator technology and anamorphic optics was tested at a channel spacing of 100 and 200 GHz, including dynamic data measurements on both single beam deflection and multi-casting to two ports. The multi-casting holograms were optimized using a modified Gerchberg-Saxton routine to design the core hologram, followed by a simulated annealing routine to reduce crosstalk at non-switched ports. The effect of clamping the magnitude of phase changes between neighboring pixels during optimization was investigated, with experimental results for multi-casting to two ports resulting in a signal insertion loss of -7.6 dB normalized to single port deflection, a uniformity of ±0.6%, and a worst case crosstalk of -19.4 dB, which can all be improved further by using a better anti-reflection coating on the LCOS SLM coverplate and other measures.

Analysis of fabricating arbitrary nanoscale patterns by LSPP direct writing lithography with two-dimensional metal hole-array

We propose to use two-dimensional metal hole-array (TMH) and spatial light modulator (SLM) technology to construct a parallel direct-writing system. SLM and movable platform are used to control the system for realizing multi-beam parallel scanning exposure to fabricate arbitrary patterns. In this system TMH is the key component which focuses the incident light beams into light spots in the photoresist by exciting local surface plasmon polariton (LSPP). Parameters of TMH are optimized to improve the focusing efficiency and transmission depth of the light spots. Theoretical analysis and numerical simulations show that the feature size and transmission depth can reach sub-80nm and 90nm, respectively, by an optimized TMH, which is feasible for parallel direct writing lithography.

Stretching single DNA molecules to demonstrate high‐force capabilities of holographic optical tweezers

The well calibrated force-extension behaviour of single double-stranded DNA molecules was used as a standard to investigate the performance of phase-only holographic optical tweezers at high forces. Specifically, the characteristic overstretch transition at 65 pN was found to appear where expected, demonstrating (1) that holographic optical trap calibration using thermal fluctuation methods is valid to high forces; (2) that the holographic optical traps are harmonic out to >250 nm of 2.1 mum particle displacement; and (3) that temporal modulations in traps induced by the spatial light modulator (SLM) do not affect the ability of optical traps to hold and steer particles against high forces. These studies demonstrate a new high-force capability for holographic optical traps achievable by SLM technologies.

Analysis and design of wide-angle foveated optical systems based on transmissive liquid crystal spatial light modulators

Optical foveated imaging using liquid crystal (LC) spatial light modulators (SLMs) has received considerable attention in recent years as a potential approach to reducing size and complexity in fast wide-angle lenses. We cover a theoretical study quantifying the diffraction efficiency and image quality of foveated optical systems (FOSs) based on transmissive LC SLMs. A practical design example of a fast wide-angle FOS based on the current transmissive LC SLM technology is proposed.