Information Encoding with Optical Dielectric Metasurface via Independent Multichannels

Recently, optical metasurfaces have attracted much attention due to their versatile features in manipulating phase, polarization, and amplitude of both reflected and transmitted light. Because it controls over four degrees of freedom: phase, polarization, amplitude, and wavelength of light wavefronts, optical cryptography is a promising technology in information security. So far, information encoding can be implemented by the metasurface in one-dimensional (1D) mode (either wavelength or polarization) and in a two-dimensional (2D) mode of both wavelength and polarization. Here, we demonstrate multiplexing multifoci optical metasurfaces for information encoding in the ultraviolet spectrum both in the 1D and 2D modes in the spatial zone, composed of high-aspect-ratio aluminum nitride nanorods, which introduce discontinuous phases through the Pancharatnam-Berry phase to realize multifoci in the spatial zone. Since the multiplexed multifocal optical metasurfaces are sensitive to the helicity of the incident light and the wavelength is within the ultraviolet spectrum, the security of the information encrypted by it would be guaranteed.

Metasurface optical holography

Refractive and conventional optical elements such as prisms and lenses are heavy, large-sized and have limited performance in light-material interactions. Due to these severe constraints, new types of structures called metasurfaces, which are composed of subwavelength structural elements with subwavelength thicknesses, are used instead of conventional and refractive based optical elements. Metasurfaces enable unprecedented control of phase, polarization, amplitude and impedance of incident light. Thanks to these very effective features, metasurfaces have gathered remarkable attention in wavefront manipulation of photons for various applications. Earlier attempts have deployed plasmonic metasurfaces in the designs. However, the light coupled to plasmons suffers from great optical loss, which restricts high transmission efficiency, at visible wavelengths due to intrinsic heat dissipation. This problem can be overcome using all dielectric structures operating mainly in the transmission mode. Here, we numerically demonstrate vortex beam generation having donut-like intensity profile and 60% transmission efficiency. In this study, we use all dielectric metasurface that is composed of thick glass substrate and crystalline silicon which is shaped as trapezoid structure at 532 nm visible wavelength. The refractive indices of glass substrate and crystalline silicon are 1.46 and 4.15 with height of 220 nm, respectively at the designed wavelength. We have achieved 0-2π phase distribution by scaling trapezoid shaped silicon at fixed height. The interface of metasurface segmented 8 regions is filled with trapezoid shaped silicon with a π/4 phase increment in an azimuthal pattern. The obtained vortex beam can be used in various applications such as light trapping, optical tweezers, and laser beam forming.

Metasurfaces have shown their unique capabilities to manipulate the phase and/or amplitude properties of incident light at the subwavelength scale, which provides an effective approach for constructing amplitude-only, phase-only or even complexed amplitude meta-devices with high resolution. Most of meta-devices control the amplitude and/or phase of the incident light with the same polarization state; however, separately controlling of amplitude and phase of the incident light with different polarization states can provide a new degree of freedom for improving the information capacity of metasurfaces and designing multifunctional meta-devices. Herein, we combine the amplitude manipulation and geometric phase manipulation by only reconfiguring the orientation angle of the nanostructure and present a single-sized design strategy for a multiplexing meta-hologram which plays the dual roles: a continuous amplitude-only meta-device and a two-step phase-only meta-device. Two different modulation types can be readily switched merely by polarization controls. Our approach opens up the possibilities for separately and independently controlling of amplitude and phase of light to construct a multiplexing meta-hologram with a single-sized metasurface, which can contribute to the advanced research and applications in multi-folded optical anti-counterfeiting, optical information hiding and optical information encoding.

In this work, we compared two methods (incipient wetness and melting) for the encapsulation of ibuprofen in the pores of Mobil Crystalline Material 41 (MCM-41) through NMR (nuclear magnetic resonance) spectroscopy. (1)H NMR spectra were recorded under very fast MAS (sample spinning 60 kHz) conditions in both 1D and 2D mode (NOESY sequence). We also performed (13)C cross-polarization magic angle spinning (CP/MAS) experiments, (13)C single pulse experiments (SPE), and (1)H-(13)C HSQC HR/MAS (heteronuclear single quantum coherence high resolution) HR/MAS correlations. Evaluation of the encapsulation methods included an analysis of the filling factor of the drug into the pores. The stability of Ibu/MCM in an environment of ethanol or water vapor was tested. Our study showed that melting a mixture of Ibu and MCM is a much more efficient method of confining the drug in the pores compared to incipient wetness. The optimal experiments for the former method achieved a filling factor of approximately 60%. We concluded that the major limitation to the applicability of the incipient wetness method (filling factor ca. 20%) is the high affinity of solvent (typically ethanol) for MCM-41. We found that even ethanol vapor can remove Ibu from the pores. When a sample of Ibu/MCM was stored for a few hours in a closed vessel with ethanol vapor, Ibu was transported from the pores to the outer walls of MCM. We observed a similar phenomenon with water vapor, although this process is slower compared to the analogous procedure using ethanol. Our study clearly demonstrates that existing methods used to encapsulate drugs in mesoporous silica nanoparticles (MSNs) require reevaluation.

Data-driven multiple removal methods have proven a valuable addition to the demultiple toolbox for three main reasons. Firstly, such methods do not make use of any a priori information about the subsurface geology and, therefore, such information cannot bias the solutions. Secondly, data-driven methods can be applied in either 1D, 2D, or 3D mode and can therefore account for the full, multidimensional complexity of the earth. Finally, because no a priori information is used, the required user interaction is minimized. These methods are now applied in production-style processing environments with comparable speed and turn-around as conventional techniques.

Metasurfaces, planar metamaterials consisting of a single layer or several layers of artificial structures, not only form the basis for fundamental physics research but also have considerable technological significance. Metasurfaces can locally modify the optical property within a subwavelength range, which can facilitate device miniaturization and system integration. Metasurfaces have shown extraordinary capabilities in the local manipulation of the light's amplitude, phase, and polarization, leading to a plethora of novel applications such as generalized Snell's law of refraction and photonic spin Hall effect. This progress report is focused on the recent advancements in the fundamental research of geometric metasurfaces and their applications in ultrathin optical devices, including planar metalenses, helicity multiplexed holograms, functionality switchable devices, polarization beam splitters, vector beam generation, arbitrary polarization control, and so on. The compactness, ease of fabrication, and unusual functionalities of these devices render geometric optical metasurface devices very attractive for new applications such as encryption, imaging, anti‐counterfeiting, optical communications, quantum science, and fundamental physics. This paper aims to bring readers some new insights, and to broaden the applications of geometric metasurfaces in more research fields of science and technology.

Flat optical components, or metasurfaces, have transformed optical imaging, data storage, information processing, and biomedical applications by providing unprecedented control over light-matter interactions. These nano-engineered structures enable compact, multidimensional manipulation of light's amplitude, phase, polarization, and wavefront, producing scalar and vector beams with unique properties such as orbital angular momentum and knotted topologies. This flexibility has potential applications in optical communication and imaging, particularly in complex environments such as atmospheric turbulence and undersea scattering. However, designing metasurfaces for shorter wavelengths, such as visible and ultraviolet light, remains challenging due to fabrication limitations and material absorption. Here, we introduce an innovative concept called topology imprinting using judiciously designed all-dielectric nonlinear optical metasurfaces to replicate desired waveforms at fundamental and harmonic frequencies, opening promising avenues for advanced photonic applications.

The standardized uptake value (SUV) is a relative measure of tracer uptake in tissue used in (18)F-FDG PET. However, the quality of ordered subset expectation maximization (OS-EM) images is sensitive to the number of iterations, because a large number of iterations leads to images with checkerboard noise. The main advantage of data acquisition in the three-dimensional (3D) mode is the high sensitivity to better exploit the intrinsic spatial resolution and the lower injection dose given to patients. In the 3D mode, the scatter fraction is higher, and, for a given administered dose, the random fraction is higher than that in the two-dimensional mode, which implies that correction methods need to be more accurate. Moreover, in clinical oncology (18)F-FDG PET studies, patients have a wide variety of body shapes and sizes, which may impact image statistics. Consequently, it is necessary to make constant the acquisition (true) counts. The purpose of this study was to optimize injection dose and acquisition time in consideration of body mass index (BMI) for 3D whole-body (18)F-FDG PET. A dedicated PET scanner, SIEMENS ECAT EXACT HR(+), was used to scan images of clinical data. The injection dose for BMI of <14-19, 19-22, 22-25, and 25< (kg/m(2)) were, 92.5 MBq, 111.0 MBq, 129.5 MBq, and 148.0 MBq, respectively. The emission scan time per bed position for BMI of <14-19, 19-22, 22-25, and >25 (kg/m(2)) were, 120, 120, 180, and 240 sec, respectively. A total of 20 patient subjects were evaluated as to true counts per bin (T/bin) of sinogram data and measured activity concentrations for the region of interest in the liver section. T/bin was stable using an optimized protocol that took into consideration the BMI for any type of body morphology. The overall coefficient of variation was 7.27% for radioactivity concentration. Additionally, Gaussian filtering (8 mm FWHM) after reconstruction by the OS-EM method provided stable SUV values even when the iteration number was increased 30 times over. Optimization of injection dose and acquisition time indicated that BMI was a clinically useful acquisition protocol for 3D whole-body (18)F-FDG PET.

Efficient and accurate phase gratings hold immense significance in the realization of large format heterodyne array receivers at terahertz frequencies. Metallic phase gratings have made substantial advancements in terms of operating wavelength and the number of diffraction beams. Like most other diffractive optical devices, metallic phase gratings are primarily optimized to operate at one specific wavelength. Metasurfaces compositing arrays of subwavelength nanostructures have been demonstrated with various optical functions, by freely modifying the polarization, phase, and amplitude of light. In this study, we present an approach to create a multi-wavelength phase grating compositing segments that incorporate multiple nanostructures. The resulting transmission phase grating not only exhibits uniform diffraction beams (2 × 2) but also achieves the same diffraction angles at both 1.31 and 2.7 THz. The measured total power efficiency of the diffraction beam pattern is 53.2% for 1.31 THz and 42.4% for 2.7 THz. These devices can be applied in terahertz astronomical observations and fluorescence microscopy applications, where multi-wavelength operation is necessary.

Metasurfaces are subwavelength structured thin films consisting of arrays of units that allow the control of polarization, phase, and amplitude of light over a subwavelength thickness. Recent developments in topological photonics have greatly broadened the horizon in designing metasurfaces for novel functional applications. In this review, we summarize recent progress in the research field of topological metasurfaces, first from the perspectives of passive and active in the classical regime, and then in the quantum regime. More specifically, we begin by examining the passive topological phenomena in two-dimensional photonic systems, including both time-reversal broken systems and time-reversal preserved systems. Subsequently, we discuss the cutting-edge studies of active topological metasurfaces, including nonlinear topological metasurfaces and reconfigurable topological metasurfaces. After overviewing topological metasurfaces in the classical regime, we show how they could provide a new platform for quantum information and quantum many-body physics. Finally, we conclude and describe some challenges and future directions of this fast-evolving field.

This study aims to evaluate the accuracy of location (x, y and z) using a Magellan GPS NAV 1000 receiver. The position of a known reference point was compared with 50 fix points measured in two-dimensional (2D) mode (x, y) and with 50 fix points measured in three-dimensional (3D) mode (x, y and z). The mean errors and the root mean square errors (RMSE) in the Euclidian distances between the reference poinl and the measured fix points were 17.9m and 20.0m respectively for the 2D measurements, and 25.7m and 34.8m respectively for the 3D measurements. The mean error in elevation was 0-2 m and the corresponding RMSE was 39.1 m. The study indicates a significant difference in the total error (Euclidian distance) between points obtained with different signal qualities and different geometric qualities. The error in the Euclidian distance never exceeded 44.0 m using 2D mode, which suggests that the Magellan GPS NAV 1000 receiver should be a useful supportive tool for many remote sensing applications.

Controlling both amplitude and phase of light in the subwavelength scale is a challenge for traditional optical devices. Here, we propose and numerically investigate a novel plasmonic meta-hologram, demonstrating broadband manipulation of both phase and amplitude in the subwavelength scale. In the meta-hologram, phase modulation is achieved by the detour phase distribution of unit cells, and amplitude is continuously modulated by a T-shaped nano-cavity with tunable plasmonic resonance. Compared to phase-only holograms, such a meta-hologram could reconstruct three-dimensional (3D) images with higher signal-to-noise ratio and better image quality, thus offering great potential in applications such as 3D displays, optical communications, and beam shaping.

Modelling and design of human eye inspired concentric cylindrical metalens

Summary A series of gravity-assisted vertical core displacements of contact-miscible and multiple-contact-miscible CO2/recombined-crude-oil systems was conducted and simulated. Gravity-assisted displacements offer the advantages of eliminating gravity tongues and stabilizing viscous fingers. Although the process has been used successfully in the field, a mechanistic laboratory and modeling study of gravity-assisted multiple-contact-miscible CO2 flooding has not been described previously. The results from this experimental and computer modeling study elucidate the complex mechanisms acting in gravity-assisted CO2 flooding. Component transfer, as occurs in multiple-contact-miscible processes, can strongly affect flood-front stability. In general, better performance is obtained from vertically downward displacements than from comparable displacements in horizontal cores. Miscibility develops at the same pressure in vertical floods and in a much shorter core length. It was further demonstrated that displacement efficiency increases at conditions where mixing of CO2 and oil is minimized. Excellent simulation of experimental recoveries and rates were obtained with a compositional simulator in a one-dimensional (1D) mode.