Search Results (140)

Metalenses, a novel class of advanced planar optical devices based on metasurfaces developed in recent years, enable the design of incident light’s amplitude, phase, and polarization with high degrees of freedom to meet application requirements. This review systematically summarizes the latest research advances in the field of metalenses. It first elucidates their fundamental physical principles and modulation mechanisms. Based on constituent materials, metalenses are categorized into plasmonic and dielectric types. Functionally, they are classified as tunable metalenses, wide-field-of-view (wide-FOV) metalenses, and achromatic metalenses, highlighting some of the most recent progress in the field. This review aims to deliver a systematic overview of metalens technology while proposing novel design paradigms for advanced optical systems. Full article

This study proposes a high-contrast photoacoustic (PA) imaging methodology based on a dual-wavelength confocal metalens, designed to monitor the dissemination of cancer cells and to inform subsequent cancer treatment strategies. The metalens is composed of two metasurfaces that perform filtering and focusing functions, effectively reducing the cross-talk between the two wavelengths of light in space and achieving a confocal effect. Furthermore, to minimize process complexity, a uniform material system of silicon dioxide (SiO₂) and titanium dioxide (TiO₂) is employed across the different metasurfaces of the metalens. The designed metalens has a radius of 25 µm and an operational focal length of 98.5 µm. The results confirm that this dual-metasurface design achieves high focusing efficiency alongside precise focusing capability, with the deviations of the actual focal lengths for both beams from the design values being within 1.5 µm. Additionally, this study developed a skin tissue model and simulated multi-wavelength photoacoustic imaging of cancer cells within the human body by integrating theories of radiative transfer, photothermal conversion, and the wave equation. The results demonstrate that the enhancement trend of the reconstructed signal closely matches the original signal, confirming the model’s excellent fitting performance. The sound pressure values generated by cancer cells are significantly higher than those of normal cells, proving that this method can effectively distinguish cancerous tissue from healthy tissue. This research provides new theoretical support and methodological foundations for the clinical application of multi-wavelength photoacoustic imaging technology. Full article

The emergence of metalenses has opened new possibilities for miniaturizing optical systems. However, the limited group delay provided by meta-atoms restricts their aperture size under broadband operation. This challenge has stimulated the development of hybrid refractive–metalens systems, which overcome the performance limitations of individual metalenses while achieving a more compact form factor than conventional refractive lens assemblies. Here, we propose a design methodology for hybrid lenses that combines ray tracing with full-wave simulation. We analyze key aspects of the metalens within the hybrid system for a wide wavelength band—specifically, dispersion and transmission efficiency. Based on this approach, we designed a high-resolution hybrid lens operating in the 435–656 nm visible band with a 35° field of view. The results demonstrate that the proposed lens achieves imaging performance equivalent to that of conventional refractive systems while reducing the total track length by 29%. This validates the effectiveness of our design method, indicating its strong potential for application in compact and lightweight optical systems. Full article

Nanostructures with the two-dimensional (2D) periodicity are attracting increasing attention due to their promising applications in planar optical devices and their potential for scalable industrial production. While Rigorous Coupled-Wave Analysis (RCWA) has proven to be an efficient electromagnetic solver for simulating the diffraction of large-scale periodic nanostructures, it has been largely applied in nanostructures with one-dimensional (1D) periodicity and suffers from potentially low computational stability. In this study, we present a step-by-step formulation of the RCWA algorithm for 2D stratified grating structures. Through dimensionality reduction, we show that the boundary conditions in 2D gratings can be transformed into forms analogous to those of 1D gratings. Additionally, we implement a hybrid matrix algorithm to enhance the computational stability of the RCWA. The stability and accuracy of the hybrid matrix-enhanced RCWA algorithm are compared with other recursive methods. An exemplary application in metalens demonstrates the effectiveness of our algorithms. Full article

Accurate and efficient prediction of the spectral responses of metasurface unit cells is key to intelligent metasurface design. Here, we propose a Shape-integrated Dual-Spectrum-aware transformer (SiDSaT) for forward prediction of metasurface responses. Trained on a large-scale simulation dataset, SiDSaT achieves a phase mean absolute error (MAE) below 0.05 across both cylindrical and cuboidal unit cells, demonstrating strong prediction accuracy and generalization. We further embedded SiDSaT into an inverse design framework and applied it to the design of single-wavelength and broadband achromatic metalenses. Results of focusing performance and dispersion control confirm the effectiveness and versatility of SiDSaT in supporting the high-precision inverse design of metasurface optical devices. This work offers a scalable and accurate approach for intelligent metasurface design across diverse shape configurations and broadband spectral ranges. Full article

This paper proposes a Fresnel-based Modified Moiré Varifocal Metalens (MMVL) addressing the inherent defocus at 0° rotation and significant focal quality degradation during varifocal operation in Traditional Moiré Varifocal Metalenses (TMVLs). The transmission function of the Fresnel-modified Moiré metalens combines a static term with a dynamic term, allowing the MMVLs to effectively overcome these limitations. Meanwhile, to minimize energy losses arising from polarization conversion and diffraction between the two metalenses, the nano-units on the metalenses are optimized by Particle Swarm Optimization (PSO) with FDTD simulations, maximizing the polarization conversion efficiency and transmittance. The simulation results demonstrate superior focal quality and stability in the MMVL throughout full rotational cycles, with super-diffraction-limited focusing maintained across all varifocal states. MMVLs have advantages in robustness; under axial distance variation (d = 0–20$d_0$, 0–3 μm), they maintain on-axis focus without deviation; with centering error (p = 0–10$p_0$, 0–3 μm), they sustain a clear focus at >36% efficiency. These results confirm that MMVLs have enhanced tolerance to manufacturing/assembly errors compared to TMVLs, delivering significantly stabilized optical performance. This advancement enables new possibilities for integrated micro-optics and optical tweezer applications. Full article

Waveguide-integrated metasurfaces offer a promising platform for ultracompact on-chip optical systems, enabling applications such as fluorescence sensing, holography, and near-eye displays. In particular, integrated achromatic metalenses that couple guided modes to free-space radiation are highly desirable for single-molecule fluorescence sensing, where high numerical aperture (NA), efficient light focusing, and consistent focal volume overlap across excitation and emission wavelengths are critical. However, designing integrated high-NA metalenses with multi-wavelength operation remains fundamentally challenging due to the wavelength-dependent propagation of guided modes. Here, we present an inverse design framework that simultaneously optimizes the geometries and positions of silicon nitride nanofins atop a slab waveguide to achieve diffraction-limited focusing at three wavelengths with unity NA. The resulting metalens outperforms conventional segmented designs in focusing efficiency and sidelobe suppression, particularly at wavelengths corresponding to the excitation and emission bands of the model fluorophore Alexa Fluor 647. Numerical analysis shows that the design yields a high molecule detection efficiency suitable for epi-fluorescence single-molecule sensing. This work highlights the potential of inverse-designed metalenses as a versatile on-chip platform for advanced applications in fluorescence spectroscopy, augmented reality, or optical trapping. Full article

On-chip spectral splitting structures with compact footprints hold tremendous potential for next-generation molecular sensing applications in the mid-infrared region. Here, we propose and theoretically investigate a carefully designed structure comprising a tilt grating and metalenses for dual-band spectral splitting with enhanced bandwidth. The tilt grating serves to separate the wavelength bands, and the metalenses following the grating guarantee a smooth transition of light into single-mode waveguides, giving rise to transmittances of 73.59% at 4 μm and 68.74% at 11 μm. The use of this tandem structure results in a significant footprint reduction and a remarkable 25.8% bandwidth enhancement over conventional approaches. The proposed spectral splitting scheme, with its broad wavelength range applicability, unlocks new pathways for on-chip simultaneous multi-target molecule detection. Full article

Optical systems with wide field-of-view (FOV) imaging capabilities are crucial for applications ranging from biomedical diagnostics to remote sensing, yet conventional wide-angle optics face integration challenges in compact platforms. Here, we present the design and experimental demonstration of a single-layer silicon carbide (SiC) metalens achieving a 90° total FOV, whose planar structure and small footprint address the challenges. This design is driven by a gradient-based numerical optimization strategy, Gradient-Optimized Phase Profile Shaping (GOPP), which optimizes the phase profile to accommodate the angle-dependent requirements. Combined with a front aperture, the GOPP-generated phase profile enables off-axis aberration control within a planar structure. Operating at 803 nm with a focal length of 1 mm (NA = 0.25), the fabricated metalens demonstrated focusing capabilities across the wide FOV, enabling effective wide-angle imaging. This work demonstrates the feasibility of using numerical optimization to realize single-layer metalens with challenging wide FOV capabilities, offering a promising route towards highly compact imagers for applications such as endoscopy and dermoscopy. Full article

Infrared imaging has gained considerable attention across diverse fields, including security, surveillance, and environmental monitoring. The need to minimize size, weight, power, and cost (SWaP-C) poses challenges for conventional optical systems like refractive lenses. Metalenses with subwavelength surface patterns have emerged as promising solutions to address these limitations. This review provides a comprehensive analysis of all-dielectric metalenses for long-wavelength infrared (LWIR) imaging applications, a critical spectral region for human detection and analytical applications (such as gas analysis). We examine the limitations of conventional infrared (IR) lens materials and highlight the performance advantages of LWIR metalenses. Key design principles, including chromatic and achromatic lens configurations, are discussed alongside their imaging performance. Additionally, we review advanced functionalities such as polarization control, multifocal capabilities, zoom, and reconfigurability. Theoretical performance limits and trade-offs are analyzed to provide insights into design optimization. We identify future challenges related to advanced design methods and fabrication techniques. LWIR metalenses can be expected to overcome the shortcomings of conventional LWIR lenses owing to meta-optics technologies, to achieve SWaP-C and advanced functionalities that cannot be achieved by conventional LWIR lenses. This review will guide researchers in academia and industry to develop LWIR metalenses to advance IR imaging technologies. Full article

Metalenses, as ultrathin planar optical devices based on metasurfaces, have attracted significant research interest in recent years due to their compact structure and versatile light manipulation, showing great potential to replace traditional lenses in specific applications. This review focuses on the fundamental principles of geometric and propagation phases of metalenses, introducing their applications in achromatic aberration correction, and emphasizing their advantages and limitations. We further discuss the application of multilayer metalenses in zoom optical systems and summarize methods such as topology optimization and inverse design to enhance the efficiency of metalenses. Special attention is given to comparing broadband and discrete achromatic correction, highlighting their respective working principles, design challenges, and practical implications. Additionally, recent advances in using deep learning for image-side aberration correction are briefly discussed. Finally, we highlight various practical applications of metalenses and discuss future research directions. Full article

This work proposes an ultrathin dual-polarized double-layer Huygens’ meta-atom, capable of generating Huygens’ resonance and achieving nearly 360° phase coverage and high transmission simultaneously. Two metalenses are designed based on the proposed meta-atom. The first is a dual-polarized metalens antenna with excellent directional radiation performance, achieving a peak gain of 30.4 dBi, an aperture efficiency of 47.8%, and a 3 dB bandwidth of 8.4% at 25 GHz. The second is a two-channel focusing metalens, with focusing efficiencies of 52.4% for x-polarization and 48.6% for y-polarization. The proposed meta-atom exhibits excellent transmission performance and offers a more flexible approach for designing transmissive devices, demonstrating significant application potential in the field of microwave communications, wireless power transfer, and imaging. Full article

Conventional metalenses struggle with chromatic aberration and narrow field of view (FOV), making it challenging to meet the dispersion requirements for large apertures and compensate off-axis aberrations for wide FOV. Here, we demonstrate a hybrid metalens module consisting of five refractive plastic lenses and a polarization-insensitive metalens to achieve broadband achromatic imaging within 400–700 nm and a wide FOV up to 100°. The system exhibits negligible variation in focal length (~1.2%) across the visible range (460–656 nm) and consistently achieves modulation transfer function (MTF) values > 0.2 at 167 lp/mm across all wavelengths and incident angles. We also demonstrate integrated lens modules that capture high-quality images from distances ranging between 0.5 and 4 m without post-processing, showcasing its potential for compact, wide-angle optical systems. Full article

Near-infrared imaging devices are extensively used in medical diagnosis, night vision, and security monitoring. However, existing traditional imaging devices rely on a bunch of refracting lenses, resulting in large, bulky imaging systems that restrict their broader utility. The emergence of flat meta-optics offers a potential solution to these limitations, but existing research on compact integrated devices based on near-infrared meta-optics is insufficient. In this study, we propose an integrated NIR imaging camera that utilizes large-size metalens with a silicon nanostructure with high transmission efficiency. Through the detection of target and animal and plant tissue samples, the ability to capture biological structures and their imaging performance was verified. Through further integration of the NIR imaging device, the device significantly reduces the size and weight of the system and optimizes the aperture to achieve excellent image brightness and contrast. Additionally, venous imaging of human skin shows the potential of the device for biomedical applications. This research has an important role in promoting the miniaturization and lightweight of near-infrared optical imaging devices, which is expected to be applied to medical testing and night vision imaging. Full article

Optical imaging systems using varifocal lenses have been widely used in many applications over the past several decades, such as machine vision devices, consumer electronic products, and medical instruments. Traditional varifocal lenses often consist of multiple solid focal length refractive optical elements. The varifocal ability is obtained by dislocating these optical elements along the optical axis over specific distances using mechanical driving mechanisms. It makes the traditional optical varifocal imaging systems suffer from bulky dimensions, slow response speed, complicated configuration, and discrete magnifications. Adaptive varifocal lenses have been a better choice to address the aforementioned limitations of traditional varifocal lenses. Dielectric elastomer actuators (DEA), which can effectively respond to an electric field and result in shape deformation, have been used to develop various adaptive lenses. This paper aims to give a brief review of adaptive varifocal lenses based on DEA. First, this paper describes the basic physical mechanism of DEA. Second, this paper reviews adaptive varifocal liquid lenses based on DEA and introduces their material, structure, and fabrication process, focusing on their unique advantages, such as fast response speed and compactness. However, despite these merits, the adaptive varifocal liquid lens still has challenges in environment stability and liquid leakage. To address these challenges, adaptive varifocal soft solid lenses based on DEA have been proposed, which are also reviewed. In addition, other adaptive varifocal lenses, including metalens, Fresnel lens, microlens array, and Alvarez lens, are also presented. Finally, the prospects and challenges for the development of adaptive varifocal lenses based on DEA are discussed. Full article