Miniaturized spectrometers utilizing a single reconfigurable photodetector (PD) are highly attractive in the infrared (IR) range due to their advantages in terms of cost, ease of integration, and reduced system complexity. However, such devices usually suffer from either limited wavelength tuning range or high spectral correlation in spectral sampling. Here, a new concept based on tunable guided mode resonances and surface plasmon resonances in a simple liquid crystal/Au stack is proposed to break the wavelength tuning range limit and simultaneously enable low spectral correlation. A chip-scale IR spectrometer using a single-pixel PbS PD is realized with a remarkably large wavelength tuning range over 850 nm (1150-2000 nm) and high fidelity (mean square error ≈0.001) in spectrum measurement. Such a novel technique is applied in plastic sorting and demonstrated remarkable improvement in sorting accuracy benefiting from its broadband property and distinct spectral responses at various sampling biases. Furthermore, a post-tuned operating mode for efficient and accurate spectroscopy is demonstrated by customizing the wavelength/bias scanning strategies, demonstrating the high flexibility of this technology. Full-vector analysis considering the interface anchoring effect and the anisotropic gradient refractive index distribution of liquid crystal is conducted to reveal the fundamental principles of broadband light modulation.

Photopolymers, especially acrylate-based ones with low cost and simple preparation, are promising materials for high-efficiency holographic gratings. However, it is still challenging to achieve high-performance gratings, due to the influences of many factors. In this work, we found that the dark reaction plays a critical role. The effect of the dark reaction on the optical properties of holographic gratings was investigated. Experimental results reveal that the diffraction efficiency of the gratings can be improved by a factor of three by involving the dark reaction process, and the highest diffraction efficiency for gratings can reach 97.8% after optimization. Therefore, the dark reaction can greatly enhance the optical performance of acrylate-based holographic gratings and other optical elements, thus holding great potential for many applications.

The use of liquid crystal spatial light modulator (LC-SLM) to manipulate the polarization of the light has been widely explored for different applications, including optical field manipulation, maskless lithography, polarization imaging, and LC planar-optics, among others. Precise polarization manipulation of LC-SLM is therefore highly demanded. Here, we introduce a high-efficiency approach for calibrating the polarization manipulation of a parallel-aligned LC-SLM. The approach revolves around the primary calibration criterion, the degree of polarization (DoP). Through parameter optimization to generate the calibration grayscale, a remarkable DoP as high as 97 % can be attained, with a sustained DoP level of up to 93.7 %. Experimental results showcase outstanding DoP uniformity in the modulated beam achieved with the calibrated LC-SLM. The root mean square error (RMSE) of polarization for modulated light from LC-SLM is about 0.018. A pixelated polarization calibration approach is proposed to enable efficient and precise programming of spatially-varying linearly polarized light (SVLPL), which can be further verified by the implementation of the Pancharatnam-Berry (PB) lens. The resolution of the fabricated LC planar optical elements with our setup can reach 1.54 μm. The programmable SVLPL with high DoP and resolution is potentially useful for many applications in planar optics and vectorial optical field manipulation.

Dynamic control of circularly polarized photoluminescence has aroused great interest in quantum optics and nanophotonics. Chiral plasmonic metasurfaces enable the manipulation of the polarization state via plasmon-photon coupling. However, current plasmonic light-emitting metasurfaces for effective deterministic modulation of spin-dependent emission at near-infrared wavelengths are underexplored in terms of dissymmetry and tunability. Here, we demonstrate a microfluidic hybrid emitting system of a suspended twisted stacking metasurface coated with PbS quantum dots. The suspended metasurface is fabricated with a single step of electron beam exposure, exhibiting a strong optical chirality of 309° μm-1 with a thickness of less than λ/10 at key spectral locations. With significant chiral-selective interactions, enhanced photoluminescence is achieved with strong dissymmetry in circular polarization. The dissymmetry factor of the induced circularly polarized emission can reach 1.54. More importantly, altering the refractive index of the surrounding medium at the bottom surface of the metasurface can effectively manipulate the chiroptical responses of the hybrid system, hence leading to chirality-reversed emission. This active hybrid emitting system could be a resultful platform for chirality-switchable light emission from achiral quantum emitters, holding great potential for anticounterfeiting, biosensing, light sources, imaging, and displays.

Liquid crystal polarization volume gratings are one kind of geometrical phase Bragg gratings. They exhibit strong polarization selectivity , high diffraction efficiency , large diffraction angles , and simple fabrication , making them ideal for augmented reality systems. In this review , we introduce the working principle and optical properties of liquid crystal polarization volume gratings. Then , we summarize the recent research progress in this research field. In addition, we particularly discuss the research of liquid crystal polarization volume gratings and their potential applications in solving key challenges for augmented reality waveguide displays. Finally , we summarize the current issues and development trends of waveguide displays based on liquid crystal polarization volume gratings.

We propose an innovative design for interdigital transducers (IDTs), enabling phase modulation of surface acoustic waves (SAWs) with a dislocated electrode structure. By designing the size and arrangement of these dislocated IDTs, a novel type of Airy SAWs can be generated, exhibiting self-accelerating, self-bending, and self-healing characteristics. The acceleration of the generated Airy SAW is 0.081 cm-1. Furthermore, particles and bubbles can be precisely manipulated using the generated Airy SAW. The proposed dislocated IDTs could be used for generation of many other types of SAWs, hence holding great promise for applications including SAW shaping, particle manipulation/sorting, and acoustic sensing/detection. Airy SAWs are generated with specially designed dislocated interdigital transducers (IDTs), exhibiting self-accelerating, self-bending, and self-healing characteristics.

Precisely controlling the optical characteristics of the microlens array (MLA) is a key issue for the MLA's fabrication and its applications. A cost-effective method for fabricating MLA with different curvatures and diameters by surface functionalization and electrohydrodynamic inkjet (E-jet) printing is proposed. The surface with self-assembled monolayers has low surface energy, which greatly improves the contact angle of the microlens. The UV-ozone treatment and neutral density filters with different optical densities are used to control the wettability of the substrates. Based on this method, the curvatures of the microlens can be controlled easily and the numerical aperture (NA) of the microlens can be adjusted from 0.18 to 0.49. Compared with traditional fabrication techniques, the method we demonstrated is flexible, low-cost, rapid, and capable of fabricating MLA with large area, high packing density, desirable NA, and diameters.

Compared to mechanical ones, liquid crystal (LC) beam deflectors present several advantages, such as non-mechanical control, compactness, and low power consumption, making them a viable alternative. In this work, we demonstrate an LC-based polarization-dependent, electrically tunable beam deflector, which is a composite blazed grating fabricated using a single-step photopolymerization-induced phase separation (PIPS) technique. We investigated the effect of different factors on the performance of the deflector, including the thickness of the upper substrate, the grating period, and the cell gap. The prepared sample demonstrated a diffraction angle of 2 degrees 6', and a diffraction efficiency of 40.0%. Unlike previous ones, our proposed fabrication technique for the LC beam deflector provides many benefits, such as simplicity, cost-effectiveness, and large-area production. (c) 2024 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

Stimuli-responsive materials have garnered substantial interest in recent years, particularly liquid crystal networks (LCNs) with sophisticatedly designed structures and morphing capabilities. Extensive efforts have been devoted to LCN structural designs spanning from two-dimensional (2D) to three-dimensional (3D) configurations and their intricate morphing behaviors through designed alignment. However, achieving microscale structures and large-area preparation necessitates the development of novel techniques capable of facilely fabricating LCN microstructures with precise control over both overall shape and alignment, enabling a 3D-to-3D shape change. Herein, a simple and cost-effective in-cell soft lithography (ICSL) technique is proposed to create LCN microstructures with customized shapes and predesigned morphing. The ICSL technique involves two sequential steps: fabricating the desired microstructure as the template by using the photopolymerization-induced phase separation (PIPS) method and reproducing the LCN microstructures through templating. Meanwhile, surface anchoring is employed to design and achieve molecular alignment, accommodating different deformation modes. With the proposed ICSL technique, cylindrical and spherical microlens arrays (CMLAs and SMLAs) have been successfully fabricated with stimulus-driven polarization-dependent focusing effects. This technique offers distinct advantages including high customizability, large-area production, and cost-effectiveness, which pave a new avenue for extensive applications in different fields, exemplified by adaptive soft micro-optics and photonics.

Diffractive optical element is advantageous for miniaturization, arraying and integration of optical systems. They have been widely used in beam shaping, diffractive imaging, generating beam arrays, spectral optimization and other aspects. Currently, the vast majority of diffractive optics are not tunable. This limits the applicability and functionality of these devices. Here we report a tunable diffractive optical element controlled by light in the visible band. The diffractive optical element consists of a square gold microarray deposited on a deformable substrate. The substrate is made of a liquid crystal elastomer. When pumped by a 532 nm laser, the substrate is deformed to change the crystal lattice. This changes the far-field diffraction pattern of the device. The proposed concept establishes a light-controlled soft platform with great potential for tunable/reconfigurable photonic devices, such as filters, couplers, holograms and structural color displays.

Microlenses or arrays are key elements in many applications.However, their construction methods involve multiple fabrication processes, thereby increasing the complexity and cost of fabrication.In this study, we demonstrate an optically anisotropic, electrically tunable liquid crystal (LC) microlens array using a simple, one-step fabrication method.The microlens array is formed via photopolymerization-induced phase separation inside a polymer/LC composite.It possesses both polarization-dependent and electrically tunable focusing and imaging properties.Without applying voltage, the microlens array has a natural focal length of 8 mm, which is a result of its inherent gradient refractive index profile.Upon applying voltage above the threshold, the LC molecules reorient along the electric field direction and the focal length of the microlens array gradually increases.Based on its superior properties, the microlens array is further used for integral imaging applications, demonstrating electrically tunable central depth plane.Such LC microlens arrays could find numerous potential applications owing to their advantageous features of being flat, ultra-thin, and tunable, including 3D displays, optical interconnects, and more.

Subwavelength‐structured metasurfaces working in visible and near‐infrared bands present a high challenge in large‐scale device fabrication. In this study, a scalable, high‐efficient, and low‐cost laser‐induced nanopatterning technique is exploited to fabricate a kind of short‐range disordered metagratings, which enables broadband polarization‐independent absorption in the visible to near‐infrared wavelength. The short‐range disorder of the laser‐induced nanogratings originates from the laser‐induced thermal effect and can be spontaneously organized during laser nanopatterning. The unique disorder can break the unidirectional characteristics of the nanogratings, which empowers the metagratings to excite coupled resonance modes. This helps to achieve near‐perfect absorption in the visible to near‐infrared band (400–1100 nm) with an excellent angular tolerance (up to 60°) and average absorptivities of 96.3% and 93.5% under the TM and TE modes, respectively. These low‐cost metagratings can potentially inspire wide applications in the fields of solar cells, sensing, and thermal emitters.

The recent synthesis and characterization of violet phosphorus (VP) demonstrate that it is the most stable allotrope of phosphorus, which could become a promising 2D layered semiconductor with potential applications in optoelectronic and electronic devices. However, experiments exploring the complex refractive index or permittivity have yet to be performed, hindering further application access. Due to the small size of the VP crystal sample available by the current growth method, the measurement for the complex refractive index is challenging. In this work, coherent acoustic phonon spectroscopy was performed first in the a–b plane using polarization-resolved pump-probe spectroscopy, revealing negligible anisotropy in the refractive index in the VIS–NIR regime (400–1000 nm). Then, the non-polarized reflectance spectra of VP films with different thicknesses on Si in the VIS–NIR regime were collected. The complex refractive index spectra were obtained by fitting the reflectance spectra with Fresnel's law considering multiple reflections in thin films. It was found that VP has high refractive indices and low extinction coefficients in the spectral range of 560–1000 nm, based on which a metasurface with VP nanodisks could achieve a high reflection band in the VIS–NIR regime by simulation. These results unveil the striking potential of VP for nanophotonics applications.

In this work, we propose an acoustically tunable plasmonic device based on liquid crystal (LC)-covered gold nanostructures. By utilizing the standing surface acoustic waves (SSAWs) to realign LC molecules, one can effectively tune the effective refractive index of LCs, and subsequently tune localized surface plasmon resonances (LSPRs) of the gold nanostructures. A 15 nm blue shift of the LSPR peak with the driving voltage of 400 mV pp is experimentally observed. Upon removal of the applied SSAWs, the LC molecules can return to their original orientation, and so does the LSPR peak. Besides the excellent reversibility, this active plasmonic device also features low power consumption and easy integration, which could find many potential applications including switches, modulators, and couplers.

Microlenses or arrays are key elements in many applications. However, their construction methods involve multiple fabrication processes, thereby increasing the complexity and cost of fabrication. In this study, we demonstrate an optically anisotropic, electrically tunable liquid crystal (LC) microlens array using a simple, one-step fabrication method. The microlens array is formed via photopolymerization-induced phase separation inside a polymer/LC composite. It possesses both polarization-dependent and electrically tunable focusing and imaging properties. Without applying voltage, the microlens array has a natural focal length of 8 mm, which is a result of its inherent gradient refractive index profile. Upon applying voltage above the threshold, the LC molecules reorient along the electric field direction and the focal length of the microlens array gradually increases. Based on its superior properties, the microlens array is further used for integral imaging applications, demonstrating electrically tunable central depth plane. Such LC microlens arrays could find numerous potential applications owing to their advantageous features of being flat, ultra-thin, and tunable, including 3D displays, optical interconnects, and more.

Due to the unique self-acceleration, self-healing, and non-diffraction properties, Airy beams have been explored extensively and found applications in various fields. It has been proven as an essential aspect to tune the trajectory of Airy beams for extensive applications. In this paper, we propose a method based on liquid crystal (LC) alignment with metasurfaces, which enables dynamic tuning of the trajectory of Airy beams. Benefiting from both the tunable property of LCs and the compact alignment of metasurfaces, we achieve a sizeable linear potential in a short distance, which leads to the effective tuning of the trajectory of Airy beams dynamically. The introduction of metasurfaces into the alignment of LCs provides a promising method to manipulate the planar optical field.

Conventionally, the fabrication of liquid crystal lenticular microlens arrays (LCLMLAs) is complicated and costly. Here, we demonstrate a one-step fabrication technique for LCLMLAs, which is prepared through the photopolymerization-induced phase separation in the LC/polymer composite. The LCLMLAs possess both polarization-dependent and electrically tunable focusing properties. Furthermore, we construct a 14-view 2D/3D switchable autostereoscopic display prototype based on a 2D LCD panel and the prepared LCLMLA, which has a viewing angle of 14° and a crosstalk of 46.2% at the optimal viewing zone. The proposed LCLMLAs have the merits of simple fabrication, large-scale production, and low cost.

Advances in thin film light-emitting devices have fueled the rapid growth of a new class of solid-state lighting devices, featuring low fabrication cost, high quantum efficiency, and broadband spectrum coverage, etc. In contrast to the conventional inorganic semiconductors that rely on lattice matched high crystalline quality substrate, solution processable thin films eliminate the dependence on the substrate, which is highly desired for the ease and versatility of integrations with foreign medium. By taking this advantage, this work developed an ultracompact solution to control the directionality of thin film emitters using integrated dielectric metasurface through one step spin-coating process. As a proof of concept, directional emissions from perovskite nanocrystal thin film, including collimated light emissions and two-dimensional beam steering, are experimentally demonstrated. Notably, our approach, where light emitters were integrated on the back side of substrate after the fabrication of metasurface, judiciously avoids any potential degradation of material optical quality caused by the multi-step nanofabrication. Therefore, it can serve as a generalized scheme to engage the advantageous properties of dielectric metasurface, including the compactness, high efficiency, and beam controllability with the emerging thin film light-emitting diodes (LEDs), which is applicable to a wide range of solution processable materials, including organic light-emitting diodes, quantum-dot light emitting diodes, polymer LEDs, and perovskite LEDs, opening up new pathways to develop low-cost and ultra-compact solid state light sources with versatile beams characteristics.

A lightweight and portable spectrometer is desirable for miniaturization and integration. The unprecedented capability of optical metasurfaces has shown much promise to perform such a task. We propose and experimentally demonstrate a compact high-resolution spectrometer with a multi-foci metalens. The novel metalens is designed based on wavelength and phase multiplexing, which can accurately map the wavelength information into its focal points located on the same plane. The measured wavelengths in the light spectra agree with simulation results upon the illumination of various incident light spectra. The uniqueness of this technique lies in the novel metalens that can simultaneously realize wavelength splitting and light focusing. The compactness and ultrathin nature of the metalens spectrometer render this technology have potential applications in on-chip integrated photonics where spectral analysis and information processing can be performed in a compact platform.

Chirality induction, transfer, and manipulation have aroused great interest in achiral nanomaterials. Here, we demonstrate strong upconverted circularly polarized luminescence from achiral core-shell upconversion nanoparticles (UCNPs) via a plasmonic chiral metasurface-induced optical chirality transfer. The Yb3+-sensitized core-shell UCNPs with good dispersity exhibit intense upconversion luminescence of Tm3+ and Nd3+ through the energy transfer process. By spin-coating the core-shell UCNPs on this chiral metasurface, strong enhancement and circular polarization modulation of upconversion luminescence can be achieved due to resonant coupling between surface plasmons and upconversion nanoparticles. In the UCNPs-on-metasurface composite, a significant upconversion luminescence enhancement can be achieved with a maximum enhancement factor of 32.63 at 878 nm and an overall enhancement factor of 11.61. The luminescence dissymmetry factor of the induced upconverted circularly polarized luminescence can reach 0.95 at the emission wavelength of 895 nm. The UCNPs-on-metasurface composite yields efficient modulation for the emission intensity and polarization of UCNPs, paving new pathways to many potential applications in imaging, sensing, and anticounterfeiting fields.