Showing papers by "Din Ping Tsai published in 2022"

Metasurface Micro/Nano-Optical Sensors: Principles and Applications.

Abstract: Metasurfaces are 2D artificial materials consisting of arrays of metamolecules, which are exquisitely designed to manipulate light in terms of amplitude, phase, and polarization state with spatial resolutions at the subwavelength scale. Traditional micro/nano-optical sensors (MNOSs) pursue high sensitivity through strongly localized optical fields based on diffractive and refractive optics, microcavities, and interferometers. Although detections of ultra-low concentrations of analytes have already been demonstrated, the label-free sensing and recognition of complex and unknown samples remain challenging, requiring multiple readouts from sensors, e.g., refractive index, absorption/emission spectrum, chirality, etc. Additionally, the reliability of detecting large, inhomogeneous biosamples may be compromised by the limited near-field sensing area from the localization of light. Here, we review recent advances in metasurface-based MNOSs and compare them with counterparts using micro-optics from aspects of physics, working principles, and applications. By virtue of underlying the physics and design flexibilities of metasurfaces, MNOSs have now been endowed with superb performances and advanced functionalities, leading toward highly integrated smart sensing platforms.

Ultra-compact snapshot spectral light-field imaging

Abstract: Ideal imaging, which is constantly pursued, requires the collection of all kinds of optical information of the objects in view, such as three-dimensional spatial information (3D) including the planar distribution and depth, and the colors, i.e., spectral information (1D). Although three-dimensional spatial imaging and spectral imaging have individually evolved rapidly, their straightforward combination is a cumbersome system, severely hindering the practical applications of four-dimensional (4D) imaging. Here, we demonstrate the ultra-compact spectral light-field imaging (SLIM) by using a transversely dispersive metalens array and a monochrome imaging sensor. With only one snapshot, the SLIM presents advanced imaging with a 4 nm spectral resolution and near-diffraction-limit spatial resolution. Consequently, visually indistinguishable objects and materials can be discriminated through SLIM, which promotes significant progress towards ideal plenoptic imaging.

Artificial Intelligence in Meta-optics

Abstract: Recent years have witnessed promising artificial intelligence (AI) applications in many disciplines, including optics, engineering, medicine, economics, and education. In particular, the synergy of AI and meta-optics has greatly benefited both fields. Meta-optics are advanced flat optics with novel functions and light-manipulation abilities. The optical properties can be engineered with a unique design to meet various optical demands. This review offers comprehensive coverage of meta-optics and artificial intelligence in synergy. After providing an overview of AI and meta-optics, we categorize and discuss the recent developments integrated by these two topics, namely AI for meta-optics and meta-optics for AI. The former describes how to apply AI to the research of meta-optics for design, simulation, optical information analysis, and application. The latter reports the development of the optical Al system and computation via meta-optics. This review will also provide an in-depth discussion of the challenges of this interdisciplinary field and indicate future directions. We expect that this review will inspire researchers in these fields and benefit the next generation of intelligent optical device design.

Vacuum ultraviolet nonlinear metalens

Abstract: Vacuum ultraviolet (VUV) light plays an essential role across science and technology, from molecular spectroscopy to nanolithography and biomedical procedures. Realizing nanoscale devices for VUV light generation and control is critical for next-generation VUV sources and systems, but the scarcity of low-loss VUV materials creates a substantial challenge. We demonstrate a metalens that both generates—by second-harmonic generation—and simultaneously focuses the generated VUV light. The metalens consists of 150-nm-thick zinc oxide (ZnO) nanoresonators that convert 394 nm (~3.15 eV) light into focused 197-nm (~6.29 eV) radiation, producing a spot 1.7 μm in diameter with a 21-fold power density enhancement as compared to the wavefront at the metalens surface. The reported metalens is ultracompact and phase-matching free, allowing substantial streamlining of VUV system design and facilitating more advanced applications. This work provides a useful platform for developing low-loss VUV components and increasing the accessibility of the VUV regime.

Optical manipulation with metamaterial structures

Abstract: Optical tweezers employing forces produced by light underpin important manipulation tools employed in numerous areas of applied and biological physics. Conventional optical tweezers are widely based on refractive optics, and they require excessive auxiliary optical elements to reshape both amplitude and phase, as well as wavevector and angular momentum of light, and thus impose limitations on the overall cost and integration of optical systems. Metamaterials can provide both electric and optically induced magnetic responses in subwavelength optical structures, and they are highly beneficial to achieve unprecedented control of light required for many applications and can open new opportunities for optical manipulation. Here, we review the recent advances in the field of optical manipulation employing the physics and concepts of metamaterials and demonstrate that metamaterial structures could not only help to advance classical operations such as trapping, transporting, and sorting of particles, but they can uncover exotic optical forces such as pulling and lateral forces. In addition, apart from optical manipulation of particles (that can also be called “meta-tweezers”), metamaterials can be powered dynamically by light to realize ingenious “meta-robots.” This review culminates with an outlook discussing future novel opportunities in this recently emerged field ranging from enhanced particle manipulation to meta-robot actuation.

Ultra-compact snapshot spectral light-field imaging

Abstract: Ideal imaging, which is constantly pursued, requires the collection of all kinds of optical information of the objects in view, such as three-dimensional spatial information (3D) including the planar distribution and depth, and the colors, i.e., spectral information (1D). Although three-dimensional spatial imaging and spectral imaging have individually evolved rapidly, their straightforward combination is a cumbersome system, severely hindering the practical applications of four-dimensional (4D) imaging. Here, we demonstrate the ultra-compact spectral light-field imaging (SLIM) by using a transversely dispersive metalens array and a monochrome imaging sensor. With only one snapshot, the SLIM presents advanced imaging with a 4 nm spectral resolution and near-diffraction-limit spatial resolution. Consequently, visually indistinguishable objects and materials can be discriminated through SLIM, which promotes significant progress towards ideal plenoptic imaging.

A Meta-device for Intelligent Depth Perception.

Abstract: The optical illusion affects depth-sensing due to the limited and specific light-field information acquired by single-lens imaging. The incomplete depth information or visual deception would cause cognitive errors. To resolve this problem, we demonstrate an intelligent and compact depth-sensing meta-device that is miniaturized, integrated, and applicable for diverse scenes in all light levels. The compact and multifunction stereo vision system adopts an array with 3600 achromatic meta-lenses and a size of 1.2 × 1.2 mm2 to measure the depth over a 30 cm range with deep-learning support. The meta-lens array can act as multiple imaging lenses to collect light field information. It can also work with a light source as an active optical device to project a structured light. The meta-lens array could serve as the core functional component of a light-field imaging system under bright conditions or a structured-light projection system in the dark. The depth information in both ways can be analyzed and extracted by the convolutional neural network. This work provides a new avenue for the applications such as autonomous driving, machine vision, human-computer interaction, augmented reality, biometric identification, etc. This article is protected by copyright. All rights reserved.

Superhybrid Mode-Enhanced Optical Torques on Mie-Resonant Particles.

Abstract: Circularly polarized light carries spin angular momentum, so it can exert an optical torque on the polarization-anisotropic particle by the spin momentum transfer. Here, we show that giant positive and negative optical torques on Mie-resonant (gain) particles arise from the emergence of superhybrid modes with magnetic multipoles and electric toroidal moments, excited by linearly polarized beams. Anomalous positive and negative torques on particles (doped with judicious amount of dye molecules) are over 800 and 200 times larger than the ordinary lossy counterparts, respectively. Meanwhile, a rotational motor can be configured by switching the s- and p-polarized beams, exhibiting opposite optical torques. These giant and reversed optical torques are unveiled for the first time in the scattering spectrum, paving another avenue toward exploring unprecedented physics of hybrid and superhybrid multipoles in metaoptics and optical manipulations.

Multifunctional Virus Manipulation with Large‐Scale Arrays of All‐Dielectric Resonant Nanocavities

Abstract: Spatial manipulation of a precise number of viruses for host cell infection is essential for the extensive studies of virus pathogenesis and evolution. Albeit optical tweezers have been advanced to the atomic level via optical cooling, it is still challenging to efficiently trap and manipulate arbitrary number of viruses in an aqueous environment, being restricted by insufficient strength of optical forces and a lack of multifunctional spatial manipulation techniques. Here, by employing the virus hopping and flexibility of moving the laser position, multifunctional virus manipulation with a large trapping area is demonstrated, enabling single or massive (a large quantity of) virus transporting, positioning, patterning, sorting, and concentrating. The enhanced optical forces are produced by the confinement of light in engineered arrays of nanocavities by fine tuning of the interference resonances, and this approach allows trapping and moving viruses down to 40 nm in size. The work paves the way to efficient and precise manipulation of either single or massive groups of viruses, opening a wide range of novel opportunities for virus pathogenesis and inhibitor development at the single‐virus level.

Emerging Trend in Unconventional Metasurfaces: From Nonlinear, Non-Hermitian to Nonclassical Metasurfaces

Abstract: Metasurfaces, benefiting from the flexibility in engineering the resonance, near-field, symmetry, and scattering properties of individual building blocks, are promising not only for a wide range of practical applications in the classical linear optical regime, but also facilitate research into new unconventional areas. Very recently, we have been witnessing the second quantum revolution in which quantum information processing and computation are becoming a reality. In this review, we will focus on some of the emerging developments of metasurfaces that work in the nonlinear, non-Hermitian, nonclassical, or quantum regime. We review some of the common principles shared by the development of these metasurfaces, including local field enhancement and the consideration of structure, lattice, and time-reversal symmetries.

Stable optical lateral forces from inhomogeneities of the spin angular momentum

Abstract: Transverse spin momentum related to the spin angular momentum (SAM) of light has been theoretically studied recently and predicted to generate an intriguing optical lateral force (OLF). Despite extensive studies, there is no direct experimental evidence of a stable OLF resulting from the dominant SAM rather than the ubiquitous spin-orbit interaction in a single light beam. Here, we theoretically unveil the nontrivial physics of SAM-correlated OLF, showing that the SAM is a dominant factor for the OLF on a nonabsorbing particle, while an additional force from the canonical (orbital) momentum is exhibited on an absorbing particle due to the spin-orbit interaction. Experimental results demonstrate the bidirectional movement of 5-μm-diameter particles on both sides of the beam with opposite spin momenta. The amplitude and sign of this force strongly depend on the polarization. Our optofluidic platform advances the exploitation of exotic forces in systems with a dominant SAM, facilitating the exploration of fascinating light-matter interactions.

Plasmonic anapole metamaterial for refractive index sensing

Abstract: Abstract Electromagnetic anapole mode is a nonradiative state of light originating from the deconstructive interference of radiation of the oscillating electric and toroidal dipole moments. The high quality anapole-related resonances can be used in enhancing nonlinear electromagnetic properties of materials and in sensor applications. In this work, we experimentally demonstrate plasmonic anapole metamaterial sensor of environmental refractive index in the optical part of the spectrum. Our results show that the sensor exhibits high sensitivity to the ambient refractive index at the level of 330 nm/RIU and noise floor of 8.7 × 10 -5 RIU. This work will pave the way for applications of anapole metamaterials in biosensing and spectroscopy.

Meta-lens in the sky

Abstract: Meta-lenses are advanced optical devices composed of artificial nano-antenna arrays. Its flat, lightweight, ultra-thin, compact, customizable, and easy-to-integrate advantages enable widely potential usages in new demands. We demonstrate a GaN based polarization-independent meta-lens-based camera on a drone. The diameter of the meta-lens is 2.6 mm, and the measured focal length is 5.03 mm under the 532 nm light incident. An array of the 750 nm height cylindrical nano-antennas with various sizes of the meta-lens provides the 2π phase modulation of the focusing phase distribution. The meta-lens is integrated with an image sensor and mounted on the drone to realize the aerial photography and landing assistance. By taking images of the specific pattern on the ground at different heights through the meta-lens, the flying height of the drone can be detected for landing and flying. We trust meta-lens-camera can reduce the weight burden for prolonging flight time. We believe the meta-lens-based optical devices for imaging and sensing is an important key for micro/nano-robots, micro air vehicles, and intelligent sensing devices in the future.

Metasurface‐Based Abrupt Autofocusing Beam for Biomedical Applications

Abstract: Manipulation and precise delivery of optical energies in the regions of interest within specimens require different strategies. Hence, proper control of input beam parameters is a prerequisite. One of the prominent methods is metasurface optics, capable of crafting properties of light at nanoscales. Here, the generation of an abrupt autofocusing (AAF) beam by a nanophotonic metasurface for biomedical applications is demonstrated. Fluorescence guided laser microprofiling of mouse cardiac samples is experimentally investigated, using the AAF beam to deliver optical energy selectively to specific locations. In addition, photocoagulation of ex vivo swine skin tissue is performed and observed through optical coherence tomography. The results show great potentials for integrating metasurface optics to realize miniature laser surgery instruments for wide applications in biomedicine.

Meta-lens light-sheet fluorescence microscopy for in vivo imaging

Abstract: Abstract Light-sheet fluorescent microscopy has become the leading technique for in vivo imaging in the fields of disease, medicine, and cell biology research. However, designing proper illumination for high image resolution and optical sectioning is challenging. Another issue is geometric constraints arising from the multiple bulky components for illumination and detection. Here, we demonstrate that those issues can be well addressed by integrating nanophotonic meta-lens as the illumination component for LSFM. The meta-lens is composed of 800-nm-thick GaN nanostructures and is designed for a light-sheet well-adapted to biological specimens such as the nematode Caenorhabditis elegans (C. elegans). With the meta-lens, the complexity of the LSFM system is significantly reduced, and it is capable of performing multicolor fluorescent imaging of live C. elegans with cellular resolution. Considering the miniature size and plane geometry of the meta-lens, our system enables a new design for LSFM to acquire in vivo images of biological specimens with high resolution.

Bound states in the continuum in plasmonic metasurfaces

Abstract: Being inspired by the structure of butterfly wings, we design and demonstrate experimentally novel types of plasmonic metasurfaces supporting high-Q collective lattice resonances (Q~89) in the mid-IR region revealed by focused light beams with large apertures.

Inverse Optical Torques on Dielectric Nanoparticles in Elliptically Polarized Light Waves.

Abstract: Elliptically polarized light waves carry the spin angular momentum (SAM), so they can exert optical torques on nanoparticles. Usually, the rotation follows the same direction as the SAM due to momentum conservation. It is counterintuitive to observe the reversal of optical torque acting on an ordinary dielectric nanoparticle illuminated by an elliptically or circularly polarized light wave. Here, we demonstrate that negative optical torques, which are opposite to the direction of SAM, can ubiquitously emerge when elliptically polarized light waves are impinged on dielectric nanoparticles obliquely. Intriguingly, the rotation can be switched between clockwise and counterclockwise directions by controlling the incident angle of light. Our study suggests a new playground to harness polarization-dependent optical force and torque for advancing optical manipulations.

Plasmonic bound states in the continuum for unpolarized weak spatially coherent light

Abstract: Plasmonic resonances empowered by bound states in the continuum (BICs) offer unprecedented opportunities to tailor light–matter interaction. However, excitation of high quality-factor ( Q -factor) quasi-BICs is often limited to collimated light at specific polarization and incident directions, rendering challenges for unpolarized focused light. The major hurdle is the lack of robustness against weak spatial coherence and poor polarization of incident light. Here, addressing this limitation, we demonstrate sharp resonances in symmetric plasmonic metasurfaces by exploiting BICs in the parameter space, offering ultraweak angular dispersion effect and polarization-independent performance. Specifically, a high- Q ( ≈ 71 ) resonance with near-perfect absorption ( > 90 % ) is obtained for the input of unpolarized focused light covering wide incident angles (from 0° to 30°). Also, giant electric and magnetic field enhancement simultaneously occurs in quasi-BICs. These results provide a way to achieve efficient near-field enhancement using focused light produced by high numerical aperture objectives.

Hyperbolic metamaterial resonator for enhancing UV laser emission

Abstract: Plasmonic structures offer a unique capability to generate electromagnetic oscillation in a tightly confined space at the metal-dielectric interface. This localized intense field can be used to significantly enhance light-matter interaction in an active material. Here, we use a hyperbolic metamaterial resonator on a UV AlGaN multiple quantum well to demonstrate a UV plasmonic nanolaser. The hyperbolic metamaterial consists of metal/dielectric multiple layer structure, which has dielectric permittivity tensor of opposite signs in two orthogonal directions. By proper design, it has an indefinite hyperbolic dispersion. We will discuss the resonator dimension design using this unique hyperbolic dispersion to enhance quantum well radiation for laser operation.

Autonomous sensing by intelligent meta-lens array

Abstract: We inspired and learned from nature to develop the meta-lens array for intelligent imaging and sensing. The design, fabrication, and applications of the intelligent meta-lens array are reported in this talk. We developed the meta-lens array based light field imaging system for digital focusing, full-color imaging, depth sensing for static and dynamic objects, and 1D to 3D edge detection. This research shows the importance of optical meta-devices for next-generation optical imaging and sensing. We believe this opens up an avenue for future applications of optical devices in micro-robotic vision, unmanned-vehicle sensing, virtual and augmented reality, drones, and miniature personal-security systems.

A meta-device for magic stairs (Conference Presentation)

Abstract: Magic stairs, a staircase loop, is a kind of optical illusion. Such cognitive paradox is an inherent defect when two-dimensional (2D) images represent high-dimensional information. For this demand, we demonstrate an intelligent depth-sensing system prototype applicable for diverse scenes, a switchable stereo vision system that adopts a 60 × 60 achromatic meta-lens array to measure depth over a 30-cm range with the support of deep learning. This system combines a light field camera and a structured light system to adapt to all light levels. The design, application, and experimental verification of the intelligent depth-sensing meta-device are reported in this talk.

Varifocal Meta-lens for Fluorescence Microscopy

Abstract: We demonstrated a Moiré meta-lens to perform fluorescence bioimaging. The focal length can be varied by tuning mutual angles. The compact design plays an important role in fluorescence microscopy and endoscopy for clinical purposes.

Short-wavelength nonlinear optical meta-device

Abstract: Optical meta-devices using metasurfaces have shown preeminent capabilities to control the optical nonlinearity and enhancing the nonlinear efficiency by arrangements of meta-atoms. With the great advantages of relaxed phase-matching requirements and CMOS compatibility for mass production, nonlinear metasurfaces can flexibly manipulate the phase, amplitude and polarization of the nonlinear waves at subwavelength scale. Various nonlinear frequency conversion processes, such as second harmonic generation (SHG), third harmonic generation (THG), have been widely realized to short wavelength such as vacuum ultraviolet (VUV) light and applied in optical communication, imaging, photochemistry and biosensing. The design, fabrication and application of the novel nonlinear optical meta-devices are reported in this talk.

Bound states in the continuum in all-plasmonic metasurfaces

Abstract: Metal nanostructures are very lossy when they interact with light, which hinders their use in optics and photonics requiring sharp resonances. Here, we will show that employing the physics of bound states in the continuum (BICs) in all-plasmonic metasurfaces can significantly reduce/eliminate the dissipation/radiation loss in metal nanostructures, resulting in high quality-factor (Q-factor) resonances. Also, we will show that butterfly-wings-inspired plasmonic structures can support high-Q surface lattice resonances under focused light excitation. These results allow for various applications requiring compact footprint with strong-light matter interaction in nanoscales, such as lasing and quantum detection.

Birth of a new baby: Photonics Insights

Abstract: Some day in September 2020, Lei Zhou got a phone call from Prof. Long Zhang, Deputy Director of the Shanghai Institute of Optics and Fine Mechanics (SIOM), Chinese Academy of Sciences, who formally invited Lei to serve as the founding co-Editor-in-Chief (Co-EIC) of a new journal that will be published by Chinese Laser Press (CLP). During the short conversation between Long and Lei, Long briefly explained to Lei why SIOM decided to launch this new journal aiming only to publish reviews in optics and photonics. The mission and vision of this new journal became clear as Ms. Lei Yang (General Manager of CLP) and her team visited Lei a week later, who expressed their strong wishes of building the journal as a globally reputable top platform (being the very first journal of this type proposed in China) for optics and photonics researchers to publish high-quality review articles and for graduate students and junior researchers to quickly follow the frontiers in optics and photonics. Lei was deeply impressed by such a fantastic idea, and totally agreed with the publishers that it is both important and timely to set up such a platform in China, since China not only has the largest group of readers but also has lots of top researchers (with the amount and quality increasing quickly in recent years) working in optics and photonics, both of whom need such a platform urgently. After talking with Ms. Yang, Lei happily accepted the position of Co-EIC. Afterwards, the Society of Photo-Optical Instrumentation Engineers (SPIE) joined as a co-publisher, which accelerated the birth of the journal greatly. It is always challenging to initiate something starting from zero, but working with editors in CLP is both pleasant and efficient. A milestone event in launching the journal is to invite Din Ping Tsai, Chair Professor in City University of Hong Kong, to serve as another founding Co-EIC of the journal, which has gained a beautiful name of Photonics Insights (PI) after many internal discussions. In the months following, we (Lei and Din Ping) worked very hard to invite top scientists from different countries to either join the editorial team or contribute high-quality invited review articles to PI. With strong support from the community, 12 leading scientists coming from six countries with expertise covering different fields in optics and photonics, agreed to join PI as Associate Editors, forming a very powerful editorial team. Working with these Associate Editors, we have successfully invited over 30 top researchers from all over the world with diversified expertise, who are committed to contributing high-quality review articles to PI. After more than two years of hard work, we finally reached the exciting moment to see the publication of the inauguration issue of PI, just like seeing the birth of a new baby. The first issue includes four excellent review articles, two full reviews and two mini-reviews written by leading figures in related fields. In the full review entitled “Information metasurfaces and intelligent metasurfaces,” Tie Jun Cui’s group introduced the concept of information metasurfaces and recent advances in designing metasurfaces using artificial intelligence technologies, and particularly discussed the close combinations of information metasurfaces and artificial intelligence to generate intelligent metasurfaces. In the mini-review entitled “Topological photonics in metamaterials,” Shuang Zhang’s group reviewed recent developments in topological photonics based on metamaterials, discussing mainly the realizations of various topological states of higher dimension synthetic spaces. In the mini-review entitled “Classical and generalized geometric phase in electromagnetic metasurfaces,” Xiangang Luo’s group overviewed the development of the geometricphase concept in optics, focusing on recent advances in continuously shaped geometric phase metasurfaces, geometric dynamic composite phase metasurfaces, and nonlinear and high-order linear PancharatnamBerry phase metasurfaces. Finally, in the full review entitled “Microcavity exciton polaritons at room temperature,”Qihua Xiong and co-authors presented a comprehensive review on recent theoretical and experimental developments of the exciton polaritons operating at room temperature, including theoretical background, descriptions of intriguing phenomena observed in various physical systems as well as accounts of optoelectronic applications. In addition to these excellent reviews on different topics, we are happy to have two commentary articles, written by Prof. Shining Zhu and Prof. Alexey Kavokin, to share with readers their thoughts and comments on the two reviews by Tie Jun Cui and Qihua Xiong, respectively. We hope that you can enjoy reading these exciting articles. Your comments and feedbacks are highly welcome. We look forward to your continuous support to PI, as authors, readers, or editors. Let us work together to build PI as a platform to share our insights, thoughts, and knowledge on cutting-edge research in optics and photonics.

Intelligent Meta-lens Array for Autonomous Sensing

Abstract: The design, fabrication, and applications of the intelligent meta-lens array are reported in this talk. We developed the meta-lens array based light field imaging system for full-color imaging, depth, edge detection and intelligent sensing.

High dimensional optical meta-devices: classical to quantum

Abstract: Optical meta-devices are composed of the collection of artificial subwavelength nanostructures. Phase, polarization, or amplitude of the incident electromagnetic waves can be manipulated by the specifically designed meta-devices. The demands of the new generation of photonics currently extend from classical to quantum optics. We report our progress in the design, fabrication, and application of the novel optical meta-devices from classical to quantum optics. We show a novel achromatic meta-lens array light field optical system for applications in imaging and sensing. We integrate a meta-lens array with a thin slice BBO nonlinear crystal to form a high-dimensional quantum entanglement optical chip. Results of the excellent mutual entanglement fidelity in 2-dimensional, 3-dimensional, and 4-dimensional experiments have successfully demonstrated the novel function of our high-dimensional optical quantum chip.

Meta-optic for Intelligent Imaging and Sensing

Abstract: We developed a meta-lens array based light field imaging system for full-color imaging, depth perception, edge detection and intelligent sensing. We reported the design, fabrication, and applications of the intelligent meta-lens.

Varifocal metalens based optical sectioning fluorescence imaging system

Abstract: Based on the Moiré effect, a pairwise ultrathin flat Moiré metalens is designed and fabricated. The diameter of the metalens is 1.6 mm. According to the mutual angles between two metasurfaces, the focal length tuning range of Moiré metalens is ~115 mm with ~40 % transmission efficiency at 532 nm. In addition, the Moiré metalens is implemented to a telecentric design to form the long axial scanning range imaging system with constant magnification. The scanning range of the telecentric imaging system is around 75 μm. The long tuning range with constant magnification is demonstrated by the imaging resolution chart that shows the lateral resolution of the system is around 2 μm. The proposed telecentric imaging system combines with structure illumination-based HiLo imaging principle to obtain the fine optical sectioning fluorescence images with invariant image contrast in the scanning range. The experiment results of the fluorescence beads show the optical sectioning capability of the system is around 7 μm. The ex-vivo fluorescence image results of the mice intestine tissue indicate that the system has the ability to obtain three different depths sectioning images. With the help of the HiLo imaging process, the defocus background noise can be suppressed, and the in focus villi detailed structure can be captured with high signal-to-noise ratio. The proposed varifocal ultrathin size of Moiré metalens has great potentials to replace the conventional bulky varifocal lens for compact system design of optical systems.

Sculpting multipoles for the optical pulling force in an unstructured light beam

Abstract: We study optical forces acting on a triangular dielectric prism illuminated by a circularly polarized light and suggest a novel approach for engineering optical pulling forces by employing multipolar modes of Mie-resonant subwavelength particles.