High Numerical Aperture Research Articles

Evaluation of spiral-shaped photonic crystal fiber’s performance in nonlinear optical applications

A spiral-shaped photonic crystal fiber (SS-PCF) is described in this research report. Here, by using finer mesh, and finite element method (FEM), the fundamental properties of optical transmission, such as nonlinearity (), birefringence (Br), beat length (), confinement loss (), numerical aperture (NA), effective mode area () are derived for wavelength range from 0.1 to 1.5 Separately employed as core materials, Gallium phosphide (GaP), Graphene, and tellurite exhibit greater performance than that of earlier works. Graphene provides the extremely high nonlinearity of 6.13 × W− 1km− 1, GaP of 3.70 × W− 1km− 1 and tellurite of 3.28 × W− 1km− 1 at 0.1. To the best of our knowledge, an SS-PCF is the first to test the performance of numerous ceramic objects in optical nonlinear applications. In actuality, the structure’s evanescent fields aid in the modeling process and display a performance profile with an ultra-high Br of 0.33, an exceptionally high NA of 0.86, and an extremely low of 1.0 × dBm− 1. All these results might be crucial in biological imaging, sensing, supercontinuum applications, polarization maintenance, optical parameter amplification, and additional nonlinear applications.

Stitching insights towards high numerical aperture extreme ultraviolet lithography: an experimental study

Stitching insights towards high numerical aperture extreme ultraviolet lithography: an experimental study

Special Section Guest Editorial: High Numerical Aperture Exposure Tools and Lithography

Special Section Guest Editorial: High Numerical Aperture Exposure Tools and Lithography

Construction of optical lattice-type skyrmion arrays in tightly focused electromagnetic field.

By utilizing the time inversion of radiation from spatial dipole arrays, we propose a method for constructing the spatial lattice-type skyrmion arrays under 4π focusing conditions, including Néel-, Bloch-, and Anti-skyrmions/merons. The Richards-Wolf vector diffraction theory is applied to analyze the radiation field emitted by dipole arrays, aiming to determine the incident field required under a high numerical aperture (NA=0.95). We construct spatial optical skyrmion arrays consisting of multiple topological points and investigate the distribution characteristics of the tightly focused field. The results indicate that diverse morphologies of optical skyrmions/merons can be achieved by adjusting the vectorial distribution within the unit dipole arrays. The high degree of freedom in combining optical skyrmion arrays holds significant potential for applications in high-density storage and precision measurement.

Highly Efficient and achromatic mid-infrared silicon nitride meta-lenses

Inverse design with topology optimization considers a promising methodology for discovering new optimized photonic structure that enables to break the limitations of the forward or the traditional design especially for the meta-structure. This work presents a high efficiency mid infra-red imaging photonics element along mid infra-red wavelengths band starts from 2 to 5 µm based on silicon nitride optimized material structures. The first two designs are broadband focusing and reflective meta-lens under very high numerical aperture condition (NA = 0.9). The two designs are modeled by inverse design with topology optimization problem with Kreisselmeier–Steinhauser (k–s) aggregation objective function, while the final design is depended on novel inverse design optimization problem with double aggregation objective function that can target bifocal points along the wavelength band producing high efficiency achromatic broadband multi-focal meta-lens under very high numerical apertures ().

Design of a high transmission illumination optics for anamorphic EUV lithography optics using deep reinforcement learning.

The design of the illumination optics for high numerical aperture (NA) anamorphic extreme ultraviolet (EUV) projection optics is a critical challenge to EUV lithography in advanced technology node. However, the EUV illumination optics design using conventional methods have flaws in illumination efficiency and illumination uniformity due to the limitations of relay configuration and matching method that can only consider one factor affecting illumination uniformity. One-mirror configuration can improve illumination efficiency by reducing the number of mirrors. Deep reinforcement learning (RL) can solve the limitations by considering multiple factors simultaneously. In this paper, a design method for a high transmission relay system and a matching method for double facets using deep RL are proposed to design NA 0.55 anamorphic EUV illumination optics. The one-mirror relay system is designed by first calculating its coaxial spherical initial configuration using matrix optics; then the one off-axis relay mirror, which is tilted and decentered to eliminate ray obscuration, is fitted into a conic surface. To satisfy the requirements of multiple factors that affect illumination uniformity, the assignment relationships between the field facets and the pupil facets are determined using deep RL under a certain illumination mode. Simulation results show that the illumination efficiency is 26.24%, and the illumination uniformity can reach 99% on the mask under different illumination modes.

Compact module for video-rate image mosaics in two-photon microscopy.

Biological applications using multiphoton microscopy increasingly seek a larger field of view while maintaining sufficient temporal sampling to observe dynamic biological processes. Multiphoton imaging also requires high numerical aperture microscope objectives to realize efficient non-linear excitation and collection of fluorescence. This combination of low-magnification and high-numerical aperture poses a challenge for system design. To address this, the use of a liquid crystal polarization grating stack is proposed here to temporally sequence through multiple fields of view. This solution pans the native field of view with minimal latency and zero inertial movement of either the microscope or biological sample. Implemented as a simple add-on unit to existing multi-photon microscopes, this device increases the total field size by 4x, covering up to 7.6mm2. Performance constraints and functional demonstration of imaging neural activity are presented.

Focusing Hemispherical Waves

The field in the focal plane of a hemispherically focused wave in an aplanatic optical system can be expressed in an analytical form. In fact, many different cases of hemispherically focused scalar and vectorial waves can be analytically expressed. We consider focusing with linear or circular polarized illumination as well as other cases such as electric dipole, transverse electric, and radial polarizations. We also investigate 4Pi focusing and the focusing of vortex waves. These results can be applied to focusing with microscope objectives of high numerical aperture.

3D Terahertz Confocal Imaging with Chromatic Metasurface

AbstractTerahertz confocal imaging allows 3D see‐through of a non‐metallic object with high resolution. Conventional methods acquiring 3D images of thick objects suffer from limited depth‐of‐field, constrained depth resolution, and/or inconsistent spatial resolution at different depths. To address these limitations, the intrinsic chromatic aberration of a typical focusing metasurface is exploited to achieve frequency‐dependent focal lengths. An object located within this extended focal range can be readily 3D inspected by performing 2D raster scans. A rigorous analysis reveals that the focal spot maintains a constant waist diameter of 2.4 mm (equivalent to 2.2 at 275 GHz) and migrates 68.1 mm (equivalent to 62.4, or 16.4 times of Rayleigh length, or 1.4‐fold of the designed focal length at 275 GHz) from 175 to 525 GHz, and thus achieving a consistent spatial resolution and a large depth‐of‐field for 3D imaging. Importantly, this large depth‐of‐field is achieved with a relatively high numerical aperture of around 0.42. Measurements conducted between 220 and 330 GHz exhibit close agreement with the calculation. To demonstrate its imaging functionality, two stacked papers with different texts, a mobile phone, and earphones concealed in a charging case are imaged, where a short‐time Fourier transform is implemented in the time‐domain terahertz images to enhance image contrast. The presented metasurface is technologically significant for imaging systems to rapidly inspect objects in 3D with exceptional resolutions. Its potential applications include in‐situ defect detection and object identification in security screening.

Convergent-beam attosecond x-ray crystallography.

Sub-ångström spatial resolution of electron density coupled with sub-femtosecond to few-femtosecond temporal resolution is required to directly observe the dynamics of the electronic structure of a molecule after photoinitiation or some other ultrafast perturbation, such as by soft X-rays. Meeting this challenge, pushing the field of quantum crystallography to attosecond timescales, would bring insights into how the electronic and nuclear degrees of freedom couple, enable the study of quantum coherences involved in molecular dynamics, and ultimately enable these dynamics to be controlled. Here, we propose to reach this realm by employing convergent-beam x-ray crystallography with high-power attosecond pulses from a hard-x-ray free-electron laser. We show that with dispersive optics, such as multilayer Laue lenses of high numerical aperture, it becomes possible to encode time into the resulting diffraction pattern with deep sub-femtosecond precision. Each snapshot diffraction pattern consists of Bragg streaks that can be mapped back to arrival times and positions of X-rays on the face of a crystal. This can span tens of femtoseconds and can be finely sampled as we demonstrate experimentally. The approach brings several other advantages, such as an increase in the number of observable reflections in a snapshot diffraction pattern, all fully integrated, to improve the speed and accuracy of serial crystallography-especially for crystals of small molecules.

საქართველოს ელექტროენერგეტიკული სისტემის დინამიკური მდგრადობის ანალიზი ბატარეის ელექტროენერგიის დამაგროვებელ სისტემებში ინტეგრირებული ორმხრივი ნახევარგამტარული გარდამსახების და ენერგიის მართვის სისტემის გამოყენებით

In practice, a directional converter integrated into the battery energy storage systems - an inverter, which only supplies energy to the network for frequency and voltage regulation when necessary, and cannot receive energy from the network. Increasing the reliability of the stability of the electric power system will be especially effective when in the battery energy storage systems will be used a Bi-directional AC/DC Converter, which in turn includes a rectifier and an inverter, which will supply the grid through the energy management system and also consume energy from it if necessary through the upgraded SCADA/EMS. The high-level architecture of the Supervisory Control and Data Acquisition systems/Energy Management System includes a number of capabilities, including a dynamic stability analysis module, also "High numerical aperture extreme ultraviolet lithography - lithography of advanced semiconductor materials" - "High-NA-EUV lithography" provides opportunities for manufacturing such microcircuits, each nanocell includes a nanotransistor and a nanocapacitor, and their chipset size is 1 nanometer. The mentioned rate of scientific development provides an opportunity to create such technologies that will give wide opportunities to modern the battery energy storage systems to fully respond to the requirements that arise during the continuous operational management of the country's electric power system.

Ultra-high numerical aperture waveguide-integrated meta beam shaper

The integration of metasurfaces with guided mode sources like waveguides has opened new frontiers for on-chip optical integration. However, the state-of-the-art in the field has targeted applications where long focal distances over thousands of light wavelengths are needed. This regime where the paraxial approximation holds enables inverse design of metasurfaces with weakly confining elements that are typically thicker than the wavelength in the material. For short focal length applications at distances less than 100λ, where the paraxial approximation fails and high numerical apertures (NAs) are necessary, a different approach is required. Here, we designed and experimentally demonstrated single-mode waveguide-integrated meta beam shapers capable of redirecting the confined light into the free space and focusing it at focal distances less than 100λ above the chip surface into a tightly focused spot. Focal spot characteristics measured at 460 nm operating wavelength approach diffraction-limited focusing across a range of focal lengths, device footprints, and numerical apertures, demonstrating the robustness of the approach. Focal volumes smaller than 1µm3 are demonstrated for a range of focal distances below 50 µm (100λ). For a device with NA of 0.95 that is one of the highest amongst integrated metasurfaces, the measured focal volume is as small as just 0.06µm3 at a focal distance of 13µm (28λ). These on-chip integrated ultra-high NA meta beam shapers have the potential to unlock new applications in quantum optical computing with trapped ions, localized optogenetic neurostimulation, and high resolution in situ microscopy.

All-reflective freeform microscope objective for ultra-broadband microscopy.

Conventional refractive microscope objective lenses have limited applicability to a range of imaging modalities due to the dispersive nature of their optical elements. Designing a conventional refractive microscope objective that provides well-corrected imaging over a broad spectral range can be challenging, if not impossible. In contrast, reflective optics are inherently achromatic, so a system composed entirely of reflective elements is free from chromatic aberrations and, as a result, can image over an ultra-wide spectral range with perfect color correction. This study explores the design space of unobscured high numerical aperture, all-reflective microscope objectives. In particular, using freeform optical elements we obviate the need for a center obscuration, rendering the objective's modulation transfer function comparable to that of refractive lens systems of similar numerical aperture. We detail the design process of the reflective objective, from determining the design specifications to the system optimization and sensitivity analysis. The outcome is an all-reflective freeform microscope objective lens with a 0.65 numerical aperture that provides diffraction-limited imaging and is compatible with the geometric constraints of commercial microscope systems.

Annular lithography for fabricating micro- and mesoscale optical structures on curved surfaces.

This paper presents an advanced exposure system that, we believe, for the first time, enables annular lithography to create micro- and mesostructures on curved surfaces. The principle of ring creation is based on an axicon zoom system whereas the exposure tool exhibits several features that enhance its performance over previous models. Its optical design features a high numerical aperture, resulting in narrow ring widths and high resolution. Additionally, the ring diameter, which can be varied between 400 µm and 8 mm, remains constant along the optical axis due to telecentric imaging. Further functional components include an observation unit for alignment and monitoring, as well as an integrated autofocus system. In addition to determining the exposure ring width (∼ 10 µm), diffractive lenses on planar substrates as well as on a spherical lens with a radius of curvature of 68.8 mm were structured. The periods of the diffractive structure varied between 60 µm and 460 µm.

High-numerical-aperture and high-efficiency polarization-based metalenses with pitch size control utilizing silicon-rich nitride.

This study investigates the role of pitch size in achieving high numerical aperture (NA) and focusing efficiency in metalens design, while demonstrating how high refractive index materials contribute to performance enhancement by enabling smaller pitch sizes through reduced filling ratios. Silicon-rich nitride (SRN) was chosen as the material platform due to its high refractive index, CMOS compatibility, and cost-effective fabrication. Two SRN-based metalenses were designed: a geometric phase metalens (GPM) and a propagation phase metalens (PPM), each evaluated at aspect ratios of 10:1 and 4:1. The GPM achieved an NA of 0.99 with focusing efficiencies of 26.6% (10:1) and 17.6% (4:1), while the PPM achieved NAs of 0.95 (10:1) and 0.97 (4:1) with focusing efficiencies of 65.6% and 32.1%, respectively. Our findings demonstrate that smaller pitch sizes reduce spatial discretization errors, enhancing phase fidelity and focusing efficiency, which is applicable to various applications such as imaging and polarimetry.

Dual-Wavelength On-Chip Integrated Metalens for Epi-Fluorescence Single-Molecule Sensing.

Single-molecule fluorescence spectroscopy offers unique capabilities for the low-concentration sensing and probing of molecular dynmics. However, employing such a methodology for versatile sensing and diagnostics under point-of-care demands device miniaturization to lab-on-a-chip size. In this study, we numerically design metalenses with high numerical aperture (NA = 1.1), which are composed of silicon nitride nanostructures deposited on a waveguide and can selectively focus guided light into an aqueous solution at two wavelengths of interest in the spectral range of 500-780 nm. Despite the severe chromatic focal shift in the lateral directions owing to the wavelength-dependent propagation constant in a waveguide, segmented on-chip metalenses provide perfectly overlapping focal volumes that meet the requirements for epi-fluorescence light collection. We demonstrate that the molecule detection efficiencies of metalenses designed for the excitation and emission wavelengths of ATTO 490LS, Alexa 555, and APC-Cy7 tandem fluorophores are sufficient to collect several thousand photons per second per molecule at modest excitation rate constants. Such sensitivity provides reliable diffusion fluorescence correlation spectroscopy analysis of single molecules on a chip to extract their concentration and diffusion properties in the nanomolar range. Achromatic on-chip metalenses open new avenues for developing ultra-compact and sensitive devices for precision medicine and environmental monitoring.

Viscocohesive hyaluronan gel enhances stability of intravital multiphoton imaging with subcellular resolution.

Multiphoton microscopy (MPM) has become a preferred technique for intravital imaging deep in living tissues with subcellular detail, where resolution and working depths are typically optimized utilizing high numerical aperture, water-immersion objectives with long focusing distances. However, this approach requires the maintenance of water between the specimen and the objective lens, which can be challenging or impossible for many intravital preparations with complex tissues and spatial arrangements. We introduce the novel use of cohesive hyaluronan gel (HG) as an immersion medium that can be used in place of water within existing optical setups to enable multiphoton imaging with equivalent quality and far superior stability. We characterize and compare imaging performance, longevity, and feasibility of preparations in various configurations. This combination of HG with MPM is highly accessible and opens the doors to new intravital imaging applications.

Differentiable design of compact imaging systems with curved Fresnel optics

Phase elements can improve the performance and reduce the size of imaging systems, thanks to the additional degrees of freedom that are offered by the independent phase gradient on top of a refractive/reflective surface. Possible implementations include diffractive elements or metasurfaces, but these suffer from diffractive dispersion. Similar optical functionality however can be provided by thin, curved Fresnel optics, which solely rely on refraction. In this study, a differentiable raytracing framework is presented that offers precise and rapid optimization of curved Fresnel surfaces, by modeling them as a combination of a distinct geometrical and refractive surface, both differentiable with respect to the imaging merit function. The method is demonstrated by designing a compact imaging and projection lens, both with high numerical aperture. The paper analyzes the impact of Fresnelizing the optimized "theoretical" surfaces on both the imaging performance and transmission efficiency. It furthermore shows how the system performance can be enhanced through dedicated post-processing steps, emphasizing the practical relevance of compact Fresnel optics.

Development of embedded graphitic-sandwich structures in single-crystal synthetic diamond via ultrafast laser micromachining

We discuss the direct fabrication of embedded, graphitized features within high-purity, synthetic single-crystal diamond through ultrafast laser micromachining for the purpose of developing diamond-based capacitive structures. As an incorporating substrate, carbon in the form of highly pure synthetic diamond offers numerous advantageous physicochemical properties, including hardness, durability, optical transparency, and extremely high electrical resistance. On the other hand, graphitic carbon can exhibit exceptionally low electrical resistance. A simple sandwich structure of a thin sheet of diamond between two sheets of graphite could, therefore, form a simple plate-type capacitive structure. For a single structure consisting of 1 μm thick plates with areal dimensions of 5 × 1 mm2 and 1 μm gaps between plates, we estimate a capacitance of 240 pF, with a 3 kV/μm breakdown voltage in diamond. ∼2500 plates thus fabricated in a ∼5 × 5 × 1 mm3 diamond chip could, therefore, store ∼300 mJ of energy. To realize this kind of structure, we employ ultrafast laser micromachining with high numerical aperture focusing and precise positioning control to disrupt the crystalline matrix of a well-confined volume within single-crystal synthetic diamond, forming embedded graphitic features. Graphitized plate regions 1 μm thick with 1 μm separations can be fabricated in this manner, and empirical I–V measurements indicate resistances in the plates as low as ∼kΩ. We also address challenges involved with fabricating closely parallel, embedded graphitic plates in thick diamond substrates, including aberration, machining time, and cracking.

Actinic mask inspection for the era of high-numerical aperture extreme ultraviolet lithography

Actinic mask inspection for the era of high-numerical aperture extreme ultraviolet lithography