Light Modulator Research Articles

The rise of electrically tunable metasurfaces.

Metasurfaces, which offer a diverse range of functionalities in a remarkably compact size, have captured the interest of both scientific and industrial sectors. However, their inherent static nature limits their adaptability for their further applications. Reconfigurable metasurfaces have emerged as a solution to this challenge, expanding the potential for diverse applications. Among the series of tunable devices, electrically controllable devices have garnered particular attention owing to their seamless integration with existing electronic equipment. This review presents recent progress reported with respect to electrically tunable devices, providing an overview of their technological development trajectory and current state of the art. In particular, we analyze the major tuning strategies and discuss the applications in spatial light modulators, tunable optical waveguides, and adaptable emissivity regulators. Furthermore, the challenges and opportunities associated with their implementation are explored, thereby highlighting their potential to bridge the gap between electronics and photonics to enable the development of groundbreaking optical systems.

Extending the operational limit of a cooled spatial light modulator exposed to 200 W average power for holographic picosecond laser materials processing

The phase range of a Spatial Light Modulator (SLM) requires full 2π response for accurate phase modulation of the incident laser wavefront to create the desired structured intensity distribution. While cooled SLM’s allow increased power exposures, degradation in performance occurs with average powers P>100 W in a Gaussian beam due to residual absorption and consequent heating of the liquid crystal (LC) layer which seriously limits the phase stroke and diffraction efficiency. By introducing a refractive flat top intensity generator ahead of a cooled SLM, we have extended the phase range to Δφ = 2π at incident power P=210 W with only a small light field depolarisation. The operational limit has therefore been extended significantly, allowing efficient, parallel laser materials processing with a high-power picosecond laser. The calculation and implementation of binary Damman gratings for multi-beam laser processing is also shown to be useful at high power exposure.

Comparative Morphological, Physiological, and Transcriptomic Analyses of Diploid and Tetraploid Wucai (Brassica campestris L.).

Polyploid plants often exhibit superior yield, stress resistance, and quality. In this study, homologous tetraploid wucai (Brassica campestris L.) was successfully obtained by spraying seedling growth points with colchicine. The morphological, cytological, and physiological characteristics of diploid and tetraploid wucai were analyzed, and transcriptomic sequencing was performed at three stages of development. Tetraploid seedings grew slowly but exhibited darker leaves, enlarged organs and cells, increased stomatal volume, decreased stomatal density, improved nutritional content, and enhanced photosynthesis. Differentially expressed genes (DEGs) identified in diploid and tetraploid plants at three stages of development were enriched in different pathways. Notably, DEGs identified in the tetraploid plants were specifically enriched in starch and sucrose metabolism, pentose and glucuronate interconversions, and ascorbate and aldarate metabolism. In addition, we found that the light green module was most relevant to ploidy, and DEGs in this module were significantly enriched in the glycolysis/gluconeogenesis and TCA cycle pathways. The differential expression of key glycolysis-associated genes at different developmental stages may be the driver of the observed differences between diploid and tetraploid wucai. This study lays a technical foundation for the development of polyploid wucai germplasm resources as well as the breeding of new varieties with improved quality, yield, and stress resistance. It also provides a good empirical reference for the genetic breeding of closely related Brassica species.

The electrically controlled dimming film of thiol-vinyl ether system with low-voltage and high contrast ratio for smart windows

As a type of smart window, polymer dispersed liquid crystal (PDLC) electrically controlled dimming film can respond to external electrical stimuli to regulate the optical flux of sunlight, reducing energy consumption. Herein, a PDLC film was prepared by systematically studying the functionalities and structural compatibility of vinyl ether and thiol compounds, and the optimal PDLC film possesses a superior contrast ratio (CR) of 196.9. When the film thickness is adjusted to 8 μm, the film saturation voltage is reduced to 6.7 V, still maintaining a high CR of 48.4. The well-designed PDLC films exhibited excellent modulation of light. The temperature difference between PDLC film and bare ITO glass can reach 4 °C under the simulated sunlight test, demonstrating the good thermal insulation performance. This smart films with low power consumption and high CR can meet the demand for active regulation of optical flux on smart windows.

Generation of UV Ellipsoidal Pulses by 3D Amplitude Shaping for Application in High-Brightness Photoinjectors

Photocathode laser pulse shaping is a crucial technology for enhancing the performance of X-ray free-electron lasers by optimizing the quality of electron beams generated from photocathodes within high-gradient radio frequency guns. By precisely shaping these laser pulses, it is possible to significantly reduce the transverse emittance of produced electron bunches. The optimal pulse shape is an ellipsoidal distribution, commonly referred to as the Kapchinskij–Vladimirskij profile. A pulse-shaping scheme utilizing a commercial Yb:KGW laser operating at 514 nm with a repetition rate of 1 MHz and duration of 260 fs has been developed for generating electron bunches with high peak and average power. This study presents the experimental realization of ellipsoidal pulses via three-dimensional amplitude shaping using spatial light modulators at 514 nm, followed by conversion to UV (257 nm) suitable for Cs 2Te photocathodes. The preservation of pulse shape and a high conversion efficiency during this process are investigated and our experiments pave the way for future emittance minimization for X-ray free-electron lasers.

Edge-Light: Exploiting Luminescent Solar Concentrators for Ambient Light Communication

A recent advance in embedded Internet of Things (IoT) exploits ambient light for wireless communication. This new paradigm enables highly efficient links via simple light modulation, but the design space has a fundamental constraint: in most State of the Art (SoA) studies, the link can only follow the propagation direction of ambient light. Consider, for example, a swarm of drones and ground robots that want to communicate with sunlight. Drone-to-robot communication could be possible because sunlight travels downwards from the air (drone) to the ground (robot), allowing drones to modulate light to send information to robots beneath them. Robot-to-robot communication, however, is not possible because sunlight does not travel sideways (parallel to the ground). To allow 'lateral communication' with ambient light, we propose using Luminescent Solar Concentrators (LSC). These optical components receive ambient light on their surface and re-direct part of the spectra towards their edges. Considering this optical property of LSC, our work has three main contributions. First, we benchmark various optical properties of LSC to assess their performance for ambient light communication. Second, we combine LSC with liquid crystal (LC) shutters to form lateral links with ambient light. Third, we test our links indoors and outdoors with artificial and natural ambient light, by enhancing two robots with our LSC transceivers and showing that they can exchange basic commands and coordinate tasks by communicating only with sunlight.

Multi frame holograms batched optimization for binary phase spatial light modulators

Phase retrieval methods used in computer generated holograms such as Gerchberg-Saxton and gradient descent give results which are prone to noise and other defects. This work builds up on the idea of time-averaging multiple hologram frames, first introduced in methods like One-Step Phase-Retrieval and Adaptive One-Step Phase-Retrieval. The proposed technique called Multi-Frame Holograms Batched Optimization uses the L-BFGS optimization algorithm to simultaneously generate a batch of binary phase holograms which result in an average reconstructed image of improved fidelity and fast algorithmic convergence, both in the Fraunhoffer and the Fresnel regimes. The results are compared to One-Step Phase-Retrieval and Adaptive One-Step Phase-Retrieval in simulation and experimentally, proving the superiority of the proposed approach. This technique can be easily extended to other spatial modulation methods.

Influence of UV-A Light Modulation on Phenol Mineralization by TiO2 Photocatalytic Process Coadjuvated with H2O2

Influence of UV-A Light Modulation on Phenol Mineralization by TiO2 Photocatalytic Process Coadjuvated with H2O2

SOC chip based smart window curtain design

Relying on the rapid development of embedded systems, it becomes possible to integrate the system hardware into the same chip, and the system on chip SOC (System on Chips) is therefore birthed. This paper will be based on the SOC hardware and software co-design and verification, through the design of intelligent curtains for the specific implementation design of a kind of application in the al-in-one multi-functional machine motherboard design, the motherboard control core using SOC chip, integrated two MCU units, through the main control screen to display the control information to achieve the intelligent window switching conversion switching through the key such as manual mode, timer mode, light control mode. This design uses Keil as the software writing platform to realize the SOC master control system based on the on-chip bus interconnection. As well as this design can effectively reduce the degree of system cumbersomeness and provide smart window design ideas.

Sodium alginate grafted phase-changing electrolyte for energy-efficient thermochromic and electrochromic synergy with uniquely tunable optical states and simultaneous Vis-NIR modulation

Conventional smart windows, limited by their single-stimulus response, often fail to meet diverse practical needs, and cannot achieve zero transmission across the Visible-NIR spectrum. Integrating thermochromic, electrochromic, and synergetic-responsiveness into a single device is both challenging and essential for effective light modulation and energy efficiency. Herein, we present a novel green phase-changing electrolyte integrated with a versatile chromogen, to create an “all-in-one” smart window. This device autonomously switches functions and can also simultaneously respond to dual-stimuli, achieving an absolute private state. The device’s tunable performance in optical contrast, switching kinetics, coloration efficiency, and cyclic stability, influenced by lattice water concentration is also meticulously assessed. Our comprehensive study highlights the device’s robust multifunctional properties, including thermal insulation, lifestyle interventions, and environmental remediation. These features make the smart window a highly energy-efficient solution with exceptional climate adaptability, such as shutting down light transmission with environmentally-benign operations and on-demand color changes. This innovative approach transforms smart windows from mere energy savers to versatile, energy-efficient systems for modern buildings. By bridging the gap between advanced materials and practical applications, our “all-in-one” smart window represents a significant advancement, paving the way for broader adoption in various environmental and energy-saving contexts.

Broad temperature range ferrielectric liquid crystal: Temperature dependencies of dielectric and electro-optical properties

Broad temperature range ferrielectric liquid crystal mixture FerriLCM-1 was previously developed in 2022 (Pozhidaev et al. 2022). In that work dielectric and electro-optical properties of the mixture were studied at room temperature. Electrically induced birefringence index reached 0.01 at a wavelength of 532 nm with response times of 300 μs. In this paper we continue the FerriLCM-1 properties investigation in a wide temperature range from the room ones till the isotropic phase transition temperature. It is found that one of the critical electric fields is almost temperature independent, while the Kerr coefficient of quadratic electro-optical effect in deformed helix ferroelectric (DHF) mode grows with temperature increase. This leads to an increase in the depth of phase modulation. Another critical electric field decreases smoothly with temperature rising. At 47–50 °C two critical electric fields merge, while temperature dependencies of all other dielectric and electro-optical parameters of the mixture are continuous and smooth functions. At about 50 °C the maximum electrically induced birefringence in DHF-mode is ΔneffE=0.022 under the applied electric field E=0.4 V/μm and with 80 μs response time. FerriLCM-1 mixture operating in the DHF-mode exhibits a giant Kerr coefficient of 1700 nm/V2 (or even up to 2900 nm/V2 at λ=400nm) at the temperature of 85 °C combined with a 50 μs response time. This is the highest value of Kkerr coefficient among liquid crystals. All these properties make ferrielectric liquid crystal mixture FerriLCM-1 suitable for solving various problems of phase modulation of light and use in low-voltage devices.

Simultaneous Dynamic Display of Meta‐Hologram and Meta‐Nanoprinting with High Frame Rate

AbstractDynamic holography can reconstruct realistic and highly interactive 3D scenes, offering a promising way for future display. Emerging metasurface with small pixel size and powerful light modulation capability demonstrates performance superior to traditional spatial light modulators, but dynamic meta‐holography with high information capacity and high frame rate remains a challenge. This paper presents a design scheme combining a preset polarization‐dependent metasurface with a high‐speed projection module to realize smooth dynamic display at multiple polarization states. With the projection module, the system can achieve dynamic meta‐holography at two orthogonal circular polarization states with 237 and 247 different holographic frames respectively, and grayscale meta‐nanoprinting at a linear polarization state with three different patterns. At the same time, the polarization multiplexed dynamic display scheme enables independent displays at three distinct polarization states with an extremely high frame rate (9523 frames per second). This advancement holds promise for applications in dynamic holographic display, optical encryption, virtual reality, and information storage.

In-situ aberration correction for Laguerre-Gaussian optical tweezers via optimization of orbit shape

We introduce a concept of aberration correction under microscopy that is based on observation of circular Brownian motion of an object driven by orbital angular momentum of a Laguerre-Gaussian (LG) beam. Following the concept, we establish an aberration-correction scheme by using a holographic optical tweezers setup equipped with a spatial light modulator that produces the LG beam as well as corrects the light wavefront. The light wavefront is modified adaptively to improve circular symmetry and uniformity of the orbit of a colloidal dielectric sphere revolving in mid-water under the irradiation of the LG beam. We reveal that the proposed scheme is sensitive to tiny phase difference of less than the accuracy of a highest-grade optical flat, 0.05λ, and is applicable to aberrations of up to the first 21 terms of the Zernike series expansion. The scheme not only improves the quality of optical tweezers but also enables to distinguish individual objective lenses assigned a common product code from difference in aberration-correction patterns. The present contribution therefore provides a useful tool for microscopy and laser fabrication in addition to the immediate application to optical trapping.

Generation of stochastic electromagnetic beams based on modified degenerate cavity lasers

This study introduces a technique for generating stochastic electromagnetic (SEM) beams using a modified degenerate cavity laser in which one mirror is substituted with a spatial light modulator (SLM). We propose two methods to manipulate the spatial coherence of SEM beams: the first involves adjusting the size of a spatial filter within the laser cavity, which alters the number of oscillating transverse modes and thus varies the spatial coherence. The second method employs phase modulation by applying a dynamic random phase to the SLM. This dual approach allows for precise control over the spatial coherence properties of SEM beams. Experimental results demonstrate the generation of SEM beams using an SLM within a modified degenerate cavity laser and reveal a correlation between two orthogonal polarization components of the beams.

Polarization-filterless polarization-sensitive polarization-multiplexed phase-shifting self-reference digital holography

I propose a phase-shifting self-reference digital holography technique in which both three-dimensional (3D) and polarization information is simultaneously obtained without any polarization filters. A Fourier-transform lens, a polarization beam splitter, and two phase-only spatial light modulators are used to simultaneously generate self-reference holograms with orthogonal polarization directions. 3D and polarization information is multiplexed in the recorded phase-shifted digital holograms and retrieved by applying polarization-selective phase-shifting interferometry and numerical refocusing. The validity of the proposed technique is experimentally demonstrated.

Untangling light in noisy luminous environments

Electric light sources, including displays and luminaires, often exhibit rapid light fluctuations called temporal light modulation (TLM). TLM can be seen as their electrical footprint. This work demonstrates that TLM can be remotely detected and used to perform in situ photometric and spectroradiometric measurements of very low light levels superimposed to intense backgrounds. Illuminance levels about 500 000 times smaller than the background were reliably measured by lock-in detection, allowing photometric measurements to be performed during daytime, even with sunny conditions. Using a new type of optical lock-in spectrometer, it becomes possible to retrieve spectral quantities through the TLM of the light source. The spectral distribution of an LED lamp was measured against a daylit background more than 1500 times brighter. Lock-in detection is an excellent technique to perform in situ measurements of electric light, even at very low level, in the presence of daylight and other background lights, opening interesting opportunities to characterize anthropogenic light pollution.

Controlled alignment imaging optical MIMO communication system based on light spot detection of arrayed light sources

Visible light communication (VLC) technology has become one of the potential key technologies for 6 G due to its unique features, such as abundant license-free spectrum, high confidentiality, and low electromagnetic interference. In this paper, an optical multiple-input multiple-output (MIMO) communication system based on imaging reception is proposed, which can improve the data transmission rate and reduce interference between different sub-channels. To overcome the problem of optical communication link alignment, in this paper, we established an imaging optical MIMO communication system with a controlled light source array (CLSA) and proposed an optical alignment strategy to address the alignment issue. The scheme decouples the constraint that the light spot cannot be aligned with the detector in the communication system under the influence of optical parameters. Based on the light spot detection CLSA module, the communication system can ensure the stability of the link alignment when the communication distance changes. Experimental results show that when the communication distance is 20-80 m, the bit error rate (BER) of the communication system remains below 10-6. The single-channel communication rate of the system is 5 Mbps, and the total communication rate is 20 Mbps through the four-channel rate multiplexing. Moreover, if the communication distance increases to the range of 80-100 m, the BER increases, but it is always lower than the forward error correction (FEC) threshold.

Ultrafast structured light through nonlinear frequency generation in an optical enhancement cavity.

The generation of shaped laser beams, or structured light, is of interest in a wide range of fields, from microscopy to fundamental physics. There are several ways to make shaped beams, most commonly using spatial light modulators comprised of pixels of liquid crystals. These methods have limitations on the wavelength, pulse duration, and average power that can be used. Here we present a method to generate shaped light that can be used at any wavelength from the UV to IR, on ultrafast pulses, and a large range of optical powers. By exploiting the frequency difference between higher-order modes, a result of the Gouy phase, and cavity mode matching, we can selectively couple into a variety of pure and composite higher-order modes. Optical cavities are used as a spatial filter and then combined with sum-frequency generation in a nonlinear crystal as the output coupler to the cavity to create ultrafast, frequency comb structured light.

Bessel beams generation with biphase transition of vanadium dioxide metasurface

Bessel beams are highly attractive due to their non-diffraction properties, parallel processing capabilities, and large capacity. However, conventional methods for generating Bessel beams, such as using spatial light modulators, axicons, and diffraction optical elements, face limitations in terms of system complexity, bulkiness, low uniformity, and limited numerical aperture (NA). In this work, we exploited the phase change material vanadium dioxide (VO2) to generate both transmitted and reflected Bessel beams. Moreover, the self-healing property of Bessel beams was verified. Our results reveal that VO2 in the insulating state achieves a transmittance of 85% in the transmitting mode, while VO2 in the metallic state exhibits a reflection efficiency of 77% in the reflecting mode. This performance indicates the potential applications in efficient switchable metasurfaces.

Electro-optical effect of unpolarized light modulation in homeoplanar structures of ferroelectric and ferrielectric liquid crystals.

A clearly expressed effect of unpolarized light electro-optical modulation by homeoplanar structures of a smectic C* ferroelectric liquid crystal (FLC) and a ferrielectric liquid crystal (FerriLC) was discovered and investigated for the first time to our knowledge. This effect of electrically controlled light scattering is insensitive to the applied voltage sign, as for polymer-dispersed nematic liquid crystals (PDLCs), but the electro-optical modulation frequency reaches the kilohertz range. Occurrence conditions and essential features of the effect, as well as its physical origin, are discussed.