Transmissive Spatial Light Modulator Research Articles

Structured polarized laser beams for controlled spiral-shaped mass transfer in azopolymer thin films

We present an approach for the realization of controlled spiral-shaped mass transfer in azopolymer thin films and the fabrication of spiral microreliefs. For such laser processing, we propose to use light fields with structured polarization distributions generated by a transmissive spatial light modulator. The projection lithography approach is utilized, transferring the pattern directly to the surface of azopolymer thin films. The shaped polarization distributions with different dependencies of the polarization vector orientation on the azimuthal angle allow us to drive surface waves on the sample along a spiral trajectory. Additionally, the ability to control the concavity of the formed microreliefs is demonstrated. This approach can be effectively modified for the direct laser fabrication of more complex nano-/micro-elements as well as their arrays.

Nonvolatile Phase-Only Transmissive Spatial Light Modulator with Electrical Addressability of Individual Pixels.

Active metasurfaces with tunable subwavelength-scale nanoscatterers are promising platforms for high-performance spatial light modulators (SLMs). Among the tuning methods, phase-change materials (PCMs) are attractive because of their nonvolatile, threshold-driven, and drastic optical modulation, rendering zero-static power, crosstalk immunity, and compact pixels. However, current electrically controlled PCM-based metasurfaces are limited to global amplitude modulation, which is insufficient for SLMs. Here, an individual-pixel addressable, transmissive metasurface is experimentally demonstrated using the low-loss PCM Sb2Se3 and doped silicon nanowire heaters. The nanowires simultaneously form a diatomic metasurface, supporting a high-quality-factor (∼406) quasi-bound-state-in-the-continuum mode. A global phase-only modulation of ∼0.25π (∼0.2π) in simulation (experiment) is achieved, showing ten times enhancement. A 2π phase shift is further obtained using a guided-mode resonance with enhanced light-Sb2Se3 interaction. Finally, individual-pixel addressability and SLM functionality are demonstrated through deterministic multilevel switching (ten levels) and tunable far-field beam shaping. Our work presents zero-static power transmissive phase-only SLMs, enabled by electrically controlled low-loss PCMs and individual meta-molecule addressable metasurfaces.

Double-sided computer-generated holography.

We present a method for computer-generated holography (CGH) in which different images are reproduced on both sides of a hologram with a single illumination source. In the proposed method, we use a transmissive spatial light modulator (SLM) and a half mirror (HM) located downstream of the SLM. The light modulated by the SLM is partially reflected by the HM, and the reflected light is modulated again by the SLM for the double-sided image reproduction. We derive an algorithm for double-sided CGH and experimentally demonstrate it.

Measurement of multi-frequency dispersions of Electromagnetically Induced Transparency windows using Spatial Light Modulator in rubidium vapor

In this letter, we have measured the dispersive profile of the multi window Electromagnetically Induced Transparency(EIT) signals in Rubidium (Rb) atomic medium at room temperature. Weak probe laser light and strong coupling light in counter propagating direction are used to excite the atomic medium via ladder type configuration of87Rb D2 line to obtain multiple EIT peaks. The uniqueness of our work is in the experimental setup which is used for the measurement of dispersion. We have used transmissive Spatial Light Modulator(SLM) in one arm of the Mach–Zehnder(M–Z) interferometer to obtain the desired phase shift between two interfering arms for the measurement of dispersive properties of multi window EIT in Rb vapor medium. One can easily obtain the phase shift without disturbing the alignment of the M-Z interferometer by using this setup.

A WDM PAM4 FSO–UWOC Integrated System With a Channel Capacity of 100 Gb/s

A wavelength-division-multiplexing (WDM) four-level pulse amplitude modulation (PAM4) free-space optical (FSO)–underwater wireless optical communication (UWOC) integrated system with a channel capacity of 100 Gb/s is proposed and attainably demonstrated. Analytic results reveal that 1.8-GHz 405-nm blue-violet-light and 1.7-GHz 450-nm blue-light laser diodes (LDs) with two-stage light injection and optoelectronic feedback techniques are competently adopted for 100 Gb/s PAM4 signal transmission through a 500-m free-space transmission with 5-m clear ocean underwater link. Combining dual-wavelength WDM scenario with PAM4 modulation, the channel capacity of FSO–UWOC integrated systems is significantly enhanced with an aggregate transmission rate of 100 Gb/s (25 Gbaud PAM4/wavelength × 2 wavelengths). With doublet lenses in FSO, laser beam reducer and transmissive spatial light modulator in UWOC, a sufficiently low bit error rate of 10−9 and acceptable PAM4 eye diagrams are acquired. This demonstrated 100 Gb/s PAM4 FSO–UWOC integrated system with a WDM scenario is advantageous for the enhancement of a high-speed optical wireless link with long-reach transmission.

Phase-only transmissive spatial light modulator based on tunable dielectric metasurface.

Rapidly developing augmented reality, solid-state light detection and ranging (LIDAR), and holographic display technologies require spatial light modulators (SLMs) with high resolution and viewing angle to satisfy increasing customer demands. Performance of currently available SLMs is limited by their large pixel sizes on the order of several micrometers. Here, we propose a concept of tunable dielectric metasurfaces modulated by liquid crystal, which can provide abrupt phase change, thus enabling pixel-size miniaturization. We present a metasurface-based transmissive SLM, configured to generate active beam steering with >35% efficiency and a large beam deflection angle of 11°. The high resolution and steering angle obtained provide opportunities to develop the next generation of LIDAR and display technologies.

P‐100: Ultra‐Large Field‐of‐View Retinal Projection Display with Vision Correction

We propose a retinal projection display that is able to merge with vision correction. Our solution is highlighted by a corrective lens coated with an array of tiled organic light‐emitting diodes and a transmissive spatial light modulator. Its design rules are set forth in detail, followed by results and discussion.

Design of retinal projection displays enabling vision correction

We propose a retinal-projection-based near-eye display that is able to merge with the vision correction for myopia. Our solution is highlighted by a corrective lens coated with an array of tiled organic light-emitting diodes and a transmissive spatial light modulator. Its design rules are set forth in detail, followed by the results and discussion regarding the field of view, modulation transfer function, contrast ratio, distortion, and simulated imaging.

Occlusion Leak Compensation for Optical See-Through Displays Using a Single-Layer Transmissive Spatial Light Modulator.

We propose an occlusion compensation method for optical see-through head-mounted displays (OST-HMDs) equipped with a singlelayer transmissive spatial light modulator (SLM), in particular, a liquid crystal display (LCD). Occlusion is an important depth cue for 3D perception, yet realizing it on OST-HMDs is particularly difficult due to the displays' semitransparent nature. A key component for the occlusion support is the SLM-a device that can selectively interfere with light rays passing through it. For example, an LCD is a transmissive SLM that can block or pass incoming light rays by turning pixels black or transparent. A straightforward solution places an LCD in front of an OST-HMD and drives the LCD to block light rays that could pass through rendered virtual objects at the viewpoint. This simple approach is, however, defective due to the depth mismatch between the LCD panel and the virtual objects, leading to blurred occlusion. This led existing OST-HMDs to employ dedicated hardware such as focus optics and multi-stacked SLMs. Contrary to these viable, yet complex and/or computationally expensive solutions, we return to the single-layer LCD approach for the hardware simplicity while maintaining fine occlusion-we compensate for a degraded occlusion area by overlaying a compensation image. We compute the image based on the HMD parameters and the background scene captured by a scene camera. The evaluation demonstrates that the proposed method reduced the occlusion leak error by 61.4% and the occlusion error by 85.7%.

Compact and high-resolution optical orbital angular momentum sorter

A compact and high-resolution optical orbital angular momentum (OAM) sorter is proposed and demonstrated. The sorter comprises a quadratic fan-out mapper and a dual-phase corrector positioned in the pupil plane and the Fourier plane, respectively. The optical system is greatly simplified compared to previous demonstrations of OAM sorting, and the performance in resolution and efficiency is maintained. A folded configuration is set up using a single reflective spatial light modulator (SLM) to demonstrate the validity of the scheme. The two phase elements are implemented on the left and right halves of the SLM and connected by a right-angle prism. Experimental results demonstrate the high resolution of the compact OAM sorter, and the current limit in efficiency can be overcome by replacing with transmissive SLMs and removing the beam splitters. This novel scheme paves the way for the miniaturization and integration of high-resolution OAM sorters.

Creating Airy beams employing a transmissive spatial light modulator.

We present a detailed study of two novel methods for shaping the light optical wavefront by employing a transmissive spatial light modulator (SLM). Conventionally, optical Airy beams are created by employing SLMs in the so-called all-phase mode. In the first method, a numerically simulated lens phase distribution is loaded directly onto the SLM, together with the cubic phase distribution. An Airy beam is generated at the focal plane of the numerical lens. We provide for the first time, to the best of our knowledge, quantitative properties of the formed Airy beam. We derive the formula for deflection of the intensity maximum of the so-formed Airy beam, which is different from the quadratic deflection typical of Airy beams. We cross-validate the derived formula by both simulations and experiment. The second method is based on the fact that a system consisting of a transmissive SLM sandwiched between two polarizers can create a transmission function with negative values. This observation alone has the potential for various other wavefront modulations where the transmission function requires negative values. As an example for this method, we demonstrate that a wavefront can be modulated by passing the SLM system with transmission function with negative values by loading an Airy function distribution directly onto the SLM. Since the Airy function is a real-valued function but also with negative values, an Airy beam can be generated by direct transfer of the Airy function distribution onto such an SLM system. In this way, an Airy beam is generated immediately behind the SLM. As both new methods do not employ a physical lens, the two setups are more compact than conventional setups for creating Airy beams. We compare the performance of the two novel methods and the properties of the created Airy beams.

Random sources for cusped beams.

We introduce two novel classes of partially coherent sources whose degrees of coherence are described by the rectangular Lorentz-correlated Schell-model (LSM) and rectangular fractional multi-Gaussian-correlated Schell-model (FMGSM) functions. Based on the generalized Collins formula, analytical expressions are derived for the spectral density distributions of these beams propagating through a stigmatic ABCD optical system. It is shown that beams belonging to both classes form the spectral density apex that is much higher and sharper than that generated by the Gaussian Schell-model (GSM) beam with a comparable coherence state. We experimentally generate these beams by using a nematic, transmissive spatial light modulator (SLM) that serves as a random phase screen controlled by a computer. The experimental data is consistent with theoretical predictions. Moreover, it is illustrated that the FMGSM beam generated in our experiments has a better focusing capacity than the GSM beam with the same coherence state. The applications that can potentially benefit from the use of novel beams range from material surface processing, to communications and sensing through random media.

Design of a dynamic dual-foveated imaging system.

A new kind of dynamic dual-foveated imaging system in the infrared band is designed and optimized in this paper. Dual-foveated imaging refers to the variation in spatial resolution at the two selected fields across the image. Such variable resolution imaging system is suitable for a variety of applications including monitoring, recognition, and remote operation of unmanned aerial vehicle. In this system, a transmissive spatial light modulator (SLM) is used as an active optical element which is located near the image plane instead of pupil plane creatively in order to divide the two selected fields.

Measuring the phase shifts produced by transmissive spatial light modulators

Measuring the phase shifts produced by transmissive spatial light modulators

Obtaining the curve “Phase shift vs gray level” of a spatial light modulator Holoeye LC2012

In this work, the process to obtain the curve “Graylevel vs phase shift” of a transmissive spatial light modulator (SLM) HoloeyeLC2012 is described. This work arises from the need that exists for having a new optical surface testing method at INAOE's Optical Workshop. The SLM was placed in one arm of a Twyman-Green interferometer. The fringe shifts in the interference patterns were produced by displaying the different gray levels in the SLM. The gray level images displayed in the SLM were divided in two equal parts, the upper part was varying the different gray levels from 0 to 255 and the lower part stayed fixed with a gray level of 0 as reference. We show the different phase shifts and the experimental interferograms. From this analysis it was found out that a noticeable phase shift can be obtained from the 50 to the 190 gray levels.

Performance of an optically addressed liquid crystal light valve and its application in optics damage protection

We report an optically addressed liquid crystal light valve, a home-made device that has solved the problem of low transmittance caused by opaque electrodes in present transmissive spatial light modulators. The operating characteristic of the light valve is analyzed. The optimum driving voltage of this device is 27 V at 300 Hz, as deduced from the equivalent electric model. Its transmittance reaches 80% and its contrast is approximately 40:1. Its dynamic performance, especially its ability to obscure laser light at programmed locations, is demonstrated. The results are in good agreement with the desired shape, which indicates that our light valve performs very well.

Full-range, complex spatial light modulator for real-time holography

We demonstrate a full-range complex and transmissive spatial light modulator (SLM) for simultaneous and independent amplitude and phase modulation of an input wave field. Arbitrary scalar complex optical fields are generated by stacking a pixelated liquid crystal display operating in phase-only (2π) modulation with passive polarization-sensitive components. The principle is based on optical combining the light fields of two neighboring phase-only modulating pixels, which were made orthogonally polarized by a structured half-wave plate, then passing through a birefringent plate to laterally shift one of the beams collinear to the other, and finally bringing to interference by a linear polarizer. Complex modulation by the proposed SLM is experimentally verified in monochrome green operation.

Integrated Optical Unit Design for the Collinear Holographic Storage System

The optical configuration proposed by Optware Corporation has the features of recording the holographic versatile disk (HVD) and backwardly retrieving CD and DVD. This paper presents a novel design that applies the technology of integrated optical unit to the HVD system. This unit comprises a holographic optical element for splitting light and generating servo signal. A transmissive spatial light modulator (SLM) with central data part and outer-ring reference part is adopted for modulating the laser beams. A new outer-ring polarizer is accompanied with the SLM. Two lasers, one with 532 nm for the HVD and the other with 650 nm for the CD/DVD, are included in the unit. Analysis for the system was performed. Simulation results show the feasibility for implementing an integrated collinear holographic system with miniaturized size

Realization of low defect density, ultrathick, strained InGaAs/GaAs multiple quantum well structures via growth on patterned GaAs (100) substrates

Growth of low defect density highly strained InxGa1−xAs/GaAs multiple quantum well (MQW) structures of thicknesses suited for application in spatial light modulator (SLM) devices operating in infrared has been thwarted by the occurrence of strain-induced defects. Exploiting the notion of strain relief at mesa edges, we report here the first realization of very low defect density MQW structures of thickness as high as 2.38 μm at x=0.20. This has opened up the possibility of realizing a variety of reflective and transmissive SLM structures which also fruitfully exploit the transparent nature of the substrate.