Liquid Crystal Spatial Light Modulator Research Articles

Background suppression structured illumination microscopy based on polarization modulation

We report a structured illumination microscopy (SIM) reconstruction method based on polarization modulation (PM), which can suppress background noise by utilizing the polarization-sensitivity properties of fluorescent dipoles. The proposed method employs a ferroelectric liquid crystal (FLC) spatial light modulator (SLM) to generate multidirectional interference patterns, and uses a combination of two liquid crystal variable phase retarders (LCVRs) and a quarter-wave plate (QWP) for flexible and rapid polarization modulation. The results of simulations and experiments demonstrate that the combination of SIM and PM effectively suppresses background noise in SIM with a slight improvement in resolution. This technique also solves the problem of structural distortion that occasionally exists in SIM and improves the accuracy of the reconstruction.

Real time simulation of atmospheric turbulence based on GPU

Simulated turbulence phase screens have been widely used in a series of optical experiments, but their speed and accuracy still need to be improved. Because of that, We use sparse spectral models for atmospheric turbulence simulation, and we use the Computational Unified Device Architecture (CUDA) to accelerate the calculation process. Finally, we load the calculated turbulence model onto the Liquid Crystal Atmospheric Turbulence Simulator (LC-ATS). The atmospheric turbulence model was used as a wavefront phase screen, and that model was deployed to the Liquid Crystal Spatial Light Modulator (LC-SLM). In 512 × 512 resolution, it takes 1.36 ms per frame, and it reaches 423 Hz on the liquid crystal on silicon (LC-OS).

Astigmatic lens approach of defocus measurement using Computer Generated Hologram

Measurement of defocus using the astigmatic lens approach is a very simple, fast and effective technique. The approach uses an astigmatic lens to incorporate astigmatism into the test beam and the measurement of defocus is done from the intensity measurement at the focal plane of the lens. The present research is on the use of computer generated hologram in the astigmatic lens approach for measuring the strength of defocus present in the test beam. The use of a computer generated hologram in conjunction with a liquid crystal spatial light modulator allows a dynamic change in the strength of astigmatism without disturbing the measurement setup. The strength of astigmatism incorporated by the astigmatic lens on the other hand is a very important parameter that determines the sensitivity, dynamic range and resilience to cross-talk of the technique. Therefore, a dynamic change in the strength of astigmatism is very important to switch to a different mode of operation as per the demand of the applications. This is not possible with an astigmatic lens as any change in the strength of astigmatism can be achieved only by replacing the lens itself, thereby disturbing the whole measurement setup. In this paper, we provide a brief discussion on the principle of an astigmatic defocus sensor followed by the process of its implementation using computer generated hologram. Simulation is carried out to validate the technique. The simulation results are further verified experimentally with the help of a proof of principle laboratory setup. The technique is validated for all three modes of operation, i.e. maximum sensitivity, higher dynamic range and resilience to cross-talk.

Control of the Optical Wavefront in Phase and Amplitude by a Single LC-SLM in a Stellar Coronagraph Aiming for Direct Exoplanet Imaging

This article presents a novel approach to actively compensate wavefront errors in both phase and amplitude using a Liquid Crystal Spatial Light Modulator (LC-SLM) for direct exoplanet imaging. This method involves controlling the wavefront to address challenges posed by stellar coronagraphy. Experimental results demonstrate successful wavefront error compensation in both phase and amplitude components. This technique shows promise for direct exoplanet imaging and may be applied onboard orbital telescopes in the future.

Ultrafast all-optical second harmonic wavefront shaping

Optical communication can be revolutionized by encoding data into the orbital angular momentum of light beams. However, state-of-the-art approaches for dynamic control of complex optical wavefronts are mainly based on liquid crystal spatial light modulators or miniaturized mirrors, which suffer from intrinsically slow (µs-ms) response times. Here, we experimentally realize a hybrid meta-optical system that enables complex control of the wavefront of light with pulse-duration limited dynamics. Specifically, by combining ultrafast polarization switching in a WSe2 monolayer with a dielectric metasurface, we demonstrate second harmonic beam deflection and structuring of orbital angular momentum on the femtosecond timescale. Our results pave the way to robust encoding of information for free space optical links, while reaching response times compatible with real-world telecom applications.

Structurally Invariant Higher-Order Ince-Gaussian Beams and Their Expansions into Hermite-Gaussian or Laguerre-Gaussian Beams

Paraxial beam modes, which propagate in space and focus without changing their transverse intensity pattern, are of great value for multiplexing transmitted data in optical communications, both in waveguides and in free space. The best-known paraxial modes are the Hermite-Gaussian and Laguerre-Gaussian beams. Here, we derive explicit analytical expressions for Ince-Gaussian (IG) beams for several first values of the indices p = 3, 4, 5, and 6. In total, we obtain expressions for the amplitudes of 24 IG beams. These formulae are written as superpositions of the Laguerre-Gaussian (LG) or Hermite-Gaussian (HG) beams, with the superposition coefficients explicitly depending on the ellipticity parameter. Due to simultaneous representation of the IG modes via the LG and HG modes, it is easy to obtain the IG modes in the limiting cases wherein the ellipticity parameter is zero or approaches infinity. The explicit dependence of the obtained expressions for the IG modes on the ellipticity parameter makes it possible to change the intensity pattern at the beam cross-section by continuously varying the parameter values. For the first time, the intensity distributions of the IG beams are obtained for negative values of the ellipticity parameter. The obtained expressions could facilitate a theoretical analysis of properties of the IG modes and could find practical applications in the numerical simulation or generation of such beams with a liquid-crystal spatial light modulator.

64 picosecond time resolved time-correlated single photon counting imaging.

High-speed imaging of dynamic scenes is a challenging and important task in many applications. However, conventional imaging methods based on charge coupled devices or complementary metal oxide semiconductors have limitations in temporal resolution and photon sensitivity. To address this problem, we propose a novel high-speed imaging scheme that combines single-pixel imaging with single photon detection and time-correlated single photon counting. Our scheme can achieve high-speed imaging with 64ps resolution by repeating the motion scenes and using binary outputs from single photon detectors. We demonstrate our scheme by reconstructing the switching process of a digital micro-mirror device and a liquid crystal spatial light modulator. Our scheme can be further improved to 1ps resolution by using a more accurate time-correlated single photon counting system. Moreover, our scheme can adapt to different speed scenes by adjusting the temporal resolution and reducing the sampling time. Our high temporal resolution imaging scheme further expands the application areas of single-pixel imaging and provides solutions for scenes requiring single photon detection and higher temporal resolution, such as reproducible chemical reaction processes imaging, cellular or sub-cellular bio imaging, single-molecule imaging of rotary motors, high-speed equipment inspection, and other periodic high-speed scenes imaging.

Measurement of phase modulation time dynamics of liquid crystal spatial light modulator

Liquid crystal spatial light modulators for precise dynamic manipulation of coherent light fields, used in diffractive optoelectronic optical data processing systems, are considered. This paper presents the results of a study of the temporal dynamics of the HoloEye PLUTO-2 VIS-016 liquid crystal spatial light modulator for analysis of light fields rate modulation. Experiments using binary phase computer generated holograms and binary focusing phase diffractive optical elements were conducted. Based on experimental data, the time characteristics of the modulator response were determined. It was found that when the rise time of the diffraction efficiency was 146 ms after the hologram displaying onto the SLM, and when switching to a new hologram, the decay time was 97 ms. These results allowed the dynamic generation of an alternating holograms at a refresh rate of 2 Hz with an interference level of –16 dB. Increasing the frequency of fringe pattern updates increases the level of interframe noise in the generated holograms, and when updated at the specification frequency, the generated distributions cannot be separated. Determining the actual frame rate based on the rise and decay times of the diffraction efficiency makes it possible to correctly calculate the minimum operating time of an information optical system containing a liquid crystal spatial light modulator.

Fast, intelligent and high-precision adaptive null interferometry for optical freeform surfaces by backpropagation.

In the past 10 years, adaptive wavefront interferometry (AWI) has been employed for measuring freeform surface profiles. However, existing AWI techniques relying on stepwise and model-free stochastic optimizations have resulted in inefficient tests. To address these issues, deterministic adaptive wavefront interferometry (DAWI) is firstly introduced in this paper based on backpropagation (BP), which employs a loss function to simultaneously reconstruct and sparsify initial incomplete interferometric fringes until they are nulled. Each iteration of BP requires two phase shifts. Through simulations, we have verified that freeform wavefront error with a peak-to-valley (PV) of up to 168 λ can be fully compensated in tens of iterations using a 1024 × 1024 pixel area of a liquid-crystal spatial light modulator. In experiments, we accomplished a null test of a freeform surface with 80% missing interference fringes in 39 iterations, resulting in a surface profile error PV of 66.22 λ and measurement error better than λ/4. The DAWI has at least 20 times fewer iterations in fringe reconstruction than the 3-step AWI methods, and nearly an order of magnitude fewer iterations in the whole process, paving the way for significantly enhanced efficiency, generality and precision in freeform surface adaptive interferometry.

Absolutely interferometric calibration of phase liquid crystal spatial light modulators using honeycomb gratings composited with Billet-split Fresnel zone plates.

The traditional interferometric calibration of phase spatial light modulators (SLM) based on interference fringes shift is easily disturbed due to environmental vibration. Here a kind of absolutely interferometric calibration of phase SLM is investigated to eliminate the disturbance using dual honeycomb gratings composited with Billet-split Fresnel zone plates (BsFZP), in which honeycomb gratings split an incident beam into three beams and the first two beams are interfered by BsFZP while the last beam is chosen as the absolute reference point. The experiments on both 532 and 632.8nm incident wavelengths were separately carried out, and the measuring accuracy was proved by a SID4 wavefront sensor. The proposed high-accuracy calibration provided the basis for SLM application scenarios with high precision.

Biochemical and Preclinical Evaluation with Synthesis and Docking Study of Pyridopyrimidines and Selenium Nanoparticle Drugs for Cancer Targeting

Abstract: The coding method of spatial light modulator is the core key of spatial light field modulation technology, and the needs of the modulation algorithm are different under the specified mode and application requirements. This paper first reviews the progress made in recent years in light field control algorithms for digital micromirror devices (DMDs) and liquid crystal spatial light modulators (LC-SLM). Based on existing algorithms, the impact of optimization methods is analyzed. Then, the application areas of the different algorithms are summarized, and the characteristics of the control algorithms are analyzed. In addition, this review highlights innovative breakthroughs achieved by using various coding schemes and spatial light modulators (SLM) to manipulate the light field. Finally, critical future challenges facing emerging control algorithm technologies are outlined, while prospects for developing SLM control algorithms are proposed.

Light Field Modulation Algorithms for Spatial Light Modulators: A Review

Abstract: The coding method of spatial light modulator is the core key of spatial light field modulation technology, and the needs of the modulation algorithm are different under the specified mode and application requirements. This paper first reviews the progress made in recent years in light field control algorithms for digital micromirror devices (DMDs) and liquid crystal spatial light modulators (LC-SLM). Based on existing algorithms, the impact of optimization methods is analyzed. Then, the application areas of the different algorithms are summarized, and the characteristics of the control algorithms are analyzed. In addition, this review highlights innovative breakthroughs achieved by using various coding schemes and spatial light modulators (SLM) to manipulate the light field. Finally, critical future challenges facing emerging control algorithm technologies are outlined, while prospects for developing SLM control algorithms are proposed.

Liquid crystal wavefront correction based on improved machine learning for free-space optical communication

In order to suppress the impact of atmosphere turbulence on the space laser communication link, the wavefront correction technology of a liquid crystal spatial light modulator (LCSLM) is studied. Combining with the control mode of the LCSLM, we propose an improved deep learning approach that restores the input image features into the wavefront and then controls the LCSLM to compensate for the phase distortion. This method does not have Zernike coefficient truncation and does not require the calculation of coefficient matrices, thus improving the accuracy and efficiency of the algorithm. At the same time, as for its powerful phase fitting ability, the LCSLM can be used as a turbulence simulator to construct datasets. During the training process of the neural networks, a calibration between the LCSLM and deep learning is established. Finally, a spatial optical coupling experimental system is built. The results show that, under different atmospheric conditions, the liquid crystal wavefront correction method has a significant improvement in terminal coupling efficiency and has certain application prospects in the field of free-space optical communication.

Smart dimming sunglasses for photophobia using spatial light modulator

We present a smart sunglasses system engineered to assist individuals experiencing photophobia, particularly those highly sensitive to light intensity. The system integrates a high dynamic range (HDR) camera and a liquid crystal spatial light modulator (SLM) to dynamically regulate light, adapting to environmental scenes by modifying pixel transmittance through a specialized control algorithm, thereby offering adaptable light management to meet the users’ visual needs. Nonetheless, a conventional occlusion mask on the SLM, intended to block incoming light, emerges blurred and insufficient due to a misaligned focal plane. To address the challenge of imprecise light filtering, we introduce an optimization algorithm that meticulously adjusts the light attenuation process, effectively diminishing excessive brightness in targeted areas without adversely impacting regions with acceptable levels of luminance.

Diffractive optical elements generation by layer-based methods for rapid and high-quality formation of 3D-objects

The article is devoted to the generation of diffractive optical elements and computer holograms for forming three-dimensional images. Possibilities of increasing the speed of diffractive optical elements generation and the quality of reconstructed 3D-objects were investigated. Four methods of optical elements generation were analyzed. The methods use division the 3D-objects into fl at layers. The quality of 3D-object reconstruction and time generation by the methods were assessed. 3D-object reconstruction from generated optical elements was modeled. Optical formation of objects was performed by displaying optical elements onto liquid crystal spatial light modulator. It was found that the best quality of reconstruction was provided by iterative parallel ping-pong and non-convex optimization methods. The optimal ratio of reconstruction quality to generation speed ratio was obtained for the parallel ping-pong method. The possibility of fast formation high-quality three-dimensional scenes consisting of dozens of layers has been demonstrated.

Research on improving holographic display quality based on phase compensation of reproduced image light energy distribution.

Liquid crystal spatial light modulator (LC-SLM) holographic display is affected by its structure, which products multi-level diffracted image with zero-order spot, resulting in low light energy utilization and poor uniformity of the reproduced image. This paper presents a method to improve the uniformity of light energy distribution in the reproduced image by using phase compensation, and the uniformity of the image can be effectively improved by using digital blazed grating to deviate the image and performing phase compensation according to the light energy distribution. Analyzing the uniformity of light energy distribution, the phase distribution is compensated, and experiments verify the phase compensation. The experimental results show that the uniformity and light energy utilization of the reproduced image after compensation has been improved. The results show that the proposed phase compensation method can be applied to both Fresnel holography and Fourier holography; both can effectively improve the uniformity and efficiency of light energy. Therefore, this method has a specific application value to enhance the quality of holographic reproduction and light field modulation based on LC-SLM.

Flexible dynamic quantitative phase imaging based on division of focal plane polarization imaging technique.

This paper proposes a flexible and accurate dynamic quantitative phase imaging (QPI) method using single-shot transport of intensity equation (TIE) phase retrieval achieved by division of focal plane (DoFP) polarization imaging technique. By exploiting the polarization property of the liquid crystal spatial light modulator (LC-SLM), two intensity images of different defocus distances contained in orthogonal polarization directions can be generated simultaneously. Then, with the help of the DoFP polarization imaging, these images can be captured with single exposure, enabling accurate dynamic QPI by solving the TIE. In addition, our approach gains great flexibility in defocus distance adjustment by adjusting the pattern loaded on the LC-SLM. Experiments on microlens array, phase plate, and living human gastric cancer cells demonstrate the accuracy, flexibility, and dynamic measurement performance for various objects. The proposed method provides a simple, flexible, and accurate approach for real-time QPI without sacrificing the field of view.

High-frame-rate reconfigurable diffractive neural network based on superpixels.

The existing implementations of reconfigurable diffractive neural networks rely on both a liquid-crystal spatial light modulator and a digital micromirror device, which results in complexity in the alignment of the optical system and a constrained computational speed. Here, we propose a superpixel diffractive neural network that leverages solely a digital micromirror device to control the neuron bias and connection. This approach considerably simplifies the optical system and achieves a computational speed of 326 Hz per neural layer. We validate our method through experiments in digit classification, achieving an accuracy of 82.6%, and action recognition, attaining a perfect accuracy of 100%. Our findings demonstrate the effectiveness of the superpixel diffractive neural network in simplifying the optical system and enhancing computational speed, opening up new possibilities for real-time optical information processing applications.

Low-cost printed holography for the generation ofstructured light.

Recently, the study of structured light fields has attracted great interest, which includes their generation and characterization techniques, as well as their application. Most of these techniques rely on the use of expensive devices, such as liquid crystal spatial light modulators or digital micromirror devices that also require specialized knowledge and software. In this work, we present a scheme for producing low-cost amplitude holograms for the generation of structured light fields. We demonstrate the feasibility of this technique by creating a variety of paraxial modes, such as the well-known Laguerre-Gaussian and Hermite-Gaussian beams. We also demonstrate the potential of our technique in solving the phase retrieval problem to generate 2D and 3D holographic images of objects. Finally, we compare our proposal with the typical generation techniques using digital micromirror devices. Our proposal will pave the path for the generation of structured light beams in more affordable ways for the application in undergrad laboratories.

High-quality tunable optical vortex arrays with multiple states of orbital angular momentum

We demonstrate the generation of high-quality optical vortex arrays (OVAs) with multiple states of orbital angular momentum (OAM) by uploading computer-generated holograms that are specially designed onto a liquid crystal spatial light modulator. The method of encoding both the amplitude and phase of an optical field into a phase-only holograms enables precise control of spatial transverse vortex modes. By combining the spiral, checkerboard and blazed-grating phase, the zero-order diffracted light can be efficiently suppressed while energy is redistributed onto higher orders to improve the quality of vortex array. Furthermore, the intensity distribution and spatial position can be flexibly modulated as well as OAM state of each vortex laser beam. It significantly increases the versatility of OAM, broadening its application in high-capacity optical communication and manipulation of multiple particles.