All-optical modulator with photonic topological insulator made of metallic quantum wells.

All-optical modulators hold significant prospects for future information processing technologies for they are able to process optical signals without the electro-optical convertor which limits the achievable modulation bandwidth. However, owing to the hardly-controlled optical backscattering in the commonly-used device geometries and the weak optical nonlinearities of the conventional material systems, constructing an all-optical modulator with a large bandwidth and a deep modulation depth in an integration manner is still challenging. Here, we propose an approach to achieving an on-chip ultrafast all-optical modulator with ultra-high modulation efficiency and a small footprint by using photonic topological insulators (PTIs) made of metallic quantum wells (MQWs).

Holographic multiplexing metasurface with twisted diffractive neural network.

As the cornerstone of AI generated content, data drives human-machine interaction and is essential for developing sophisticated deep learning agents. Nevertheless, the associated data storage poses a formidable challenge from conventional energy-intensive planar storage, high maintenance cost, and the susceptibility to electromagnetic interference. In this work, we introduce the concept of metasurface disk, meta-disk, to expand the capacity limits of optical holographic storage by leveraging uncorrelated structural twist.

The interplay of hematite and photic biofilm triggers the acceleration of biotic nitrate removal.

The soil-water interface is replete with photic biofilm and iron minerals; however, the potential of how iron minerals promote biotic nitrate removal is still unknown. This study investigates the physiological and ecological responses of photic biofilm to hematite (FeO), in order to explore a practically feasible approach for in-situ nitrate removal. The nitrate removal by photic biofilm was significantly higher in the presence of FeO (92.

Large area single crystal gold of single nanometer thickness for nanophotonics.

Two-dimensional single crystal metals, in which the behavior of highly confined optical modes is intertwined with quantum phenomena, are highly sought after for next-generation technologies. Here, we report large area (>10 μm), single crystal two-dimensional gold flakes (2DGFs) with thicknesses down to a single nanometer level, employing an atomic-level precision chemical etching approach. The decrease of the thickness down to such scales leads to the quantization of the electronic states, endowing 2DGFs with quantum-confinement-augmented optical nonlinearity, particularly leading to more than two orders of magnitude enhancement in harmonic generation compared with their thick polycrystalline counterparts.

Large second-order susceptibility from a quantized indium tin oxide monolayer.

Due to their high optical transparency and electrical conductivity, indium tin oxide thin films are a promising material for photonic circuit design and applications. However, their weak optical nonlinearity has been a substantial barrier to nonlinear signal processing applications. In this study, we show that an atomically thin (~1.

Resonant inelastic tunneling using multiple metallic quantum wells.

Tunnel nanojunctions based on inelastic electron tunneling (IET) have been heralded as a breakthrough for ultra-fast integrated light sources. However, the majority of electrons tend to tunnel through a junction elastically, resulting in weak photon-emission power and limited efficiency, which have hindered their practical applications to date. Resonant tunneling has been proposed as a way to alleviate this limitation, but photon-emissions under resonant tunneling conditions have remained unsatisfactory for practical IET-based light sources due to the inherent contradiction between high photon-emission efficiency and power.

Dynamic recognition and mirage using neuro-metamaterials.

Breakthroughs in the field of object recognition facilitate ubiquitous applications in the modern world, ranging from security and surveillance equipment to accessibility devices for the visually impaired. Recently-emerged optical computing provides a fundamentally new computing modality to accelerate its solution with photons; however, it still necessitates digital processing for in situ application, inextricably tied to Moore's law. Here, from an entirely optical perspective, we introduce the concept of neuro-metamaterials that can be applied to realize a dynamic object- recognition system.

Highly-efficient electrically-driven localized surface plasmon source enabled by resonant inelastic electron tunneling.

On-chip plasmonic circuitry offers a promising route to meet the ever-increasing requirement for device density and data bandwidth in information processing. As the key building block, electrically-driven nanoscale plasmonic sources such as nanoLEDs, nanolasers, and nanojunctions have attracted intense interest in recent years. Among them, surface plasmon (SP) sources based on inelastic electron tunneling (IET) have been demonstrated as an appealing candidate owing to the ultrafast quantum-mechanical tunneling response and great tunability.

Kerr Metasurface Enabled by Metallic Quantum Wells.

Optical metasurfaces have emerged as promising candidates for multifunctional devices. Dynamically reconfigurable metasurfaces have been introduced by employing phase-change materials or by applying voltage, heat, or strain. While existing metasurfaces exhibit appealing properties, they do not express any significant nonlinear effects due to the negligible nonlinear responses from the typical materials used to build the metasurface.

Metasurface enabled quantum edge detection.

Metasurfaces consisting of engineered dielectric or metallic structures provide unique solutions to realize exotic phenomena including negative refraction, achromatic focusing, electromagnetic cloaking, and so on. The intersection of metasurface and quantum optics may lead to new opportunities but is much less explored. Here, we propose and experimentally demonstrate that a polarization-entangled photon source can be used to switch ON or OFF the optical edge detection mode in an imaging system based on a high-efficiency dielectric metasurface.

Two-dimensional optical spatial differentiation and high-contrast imaging.

Optical analog signal processing technology has been widely studied and applied in a variety of science and engineering fields, with the advantages of overcoming the low-speed and high-power consumption associated with its digital counterparts. Much attention has been given to emerging metasurface technology in the field of optical imaging and processing systems. Here, we demonstrate, for the first time, broadband two-dimensional spatial differentiation and high-contrast edge imaging based on a dielectric metasurface across the whole visible spectrum.

Nanoscale optical pulse limiter enabled by refractory metallic quantum wells.

The past several decades have witnessed rapid development of high-intensity, ultrashort pulse lasers, enabling deeper laboratory investigation of nonlinear optics, plasma physics, and quantum science and technology than previously possible. Naturally, with their increasing use, the risk of accidental damage to optical detection systems rises commensurately. Thus, various optical limiting mechanisms and devices have been proposed.

A spin controlled wavefront shaping metasurface with low dispersion in visible frequencies.

Similar to amplitude and phase, optical spin plays an important and non-trivial role in optics, which has been widely demonstrated in wavefront engineering, creation of new optical components, and sensitive optical metrology. In this work, we propose and experimentally demonstrate a new type of spin controlled wavefront shaping metasurface. The proposed geometric phase metasurface is designed by employing the integrated and interleaved structures to independently control the left-handed and right-handed spin components.

Optical edge detection based on high-efficiency dielectric metasurface.

Optical edge detection is a useful method for characterizing boundaries, which is also in the forefront of image processing for object detection. As the field of metamaterials and metasurface is growing fast in an effort to miniaturize optical devices at unprecedented scales, experimental realization of optical edge detection with metamaterials remains a challenge and lags behind theoretical proposals. Here, we propose a mechanism of edge detection based on a Pancharatnam-Berry-phase metasurface.

Large optical nonlinearity enabled by coupled metallic quantum wells.

New materials that exhibit strong second-order optical nonlinearities at a desired operational frequency are of paramount importance for nonlinear optics. Giant second-order susceptibility has been obtained in semiconductor quantum wells (QWs). Unfortunately, the limited confining potential in semiconductor QWs causes formidable challenges in scaling such a scheme to the visible/near-infrared (NIR) frequencies for more vital nonlinear-optic applications.

Assessment of aging characteristics of female condylar trabecular structure by cone-beam computed tomography.

Objectives: This study was performed to analyze the aging-related changes of the female condylar bone mineral density (BMD) and trabecular structure by cone-beam computed tomography (CBCT), and determine whether the condylar structure shows obvious changes after menopause.

Methods: The CBCT images of 160 female patients who met the inclusion criteria for the study were collected and divided into four groups by age (20-29 years, 30-39 years, premenopausal, and postmenopausal groups). Computer processing software CT-Analyser (Version 1.

Experimental Demonstration of Hyperbolic Metamaterial Assisted Illumination Nanoscopy.

An optical metamaterial is capable of manipulating light in nanometer scale that goes beyond what is possible with conventional materials. Taking advantage of this special property, metamaterial-assisted illumination nanoscopy (MAIN) possesses tremendous potential to extend the resolution far beyond conventional structured illumination microscopy. Among the available MAIN designs, hyperstructured illumination that utilizes strong dispersion of a hyperbolic metamaterial (HMM) is one of the most promising and practical approaches, but it is only theoretically studied.

Controlled Homoepitaxial Growth of Hybrid Perovskites.

Organic-inorganic hybrid perovskites have demonstrated tremendous potential for the next-generation electronic and optoelectronic devices due to their remarkable carrier dynamics. Current studies are focusing on polycrystals, since controlled growth of device compatible single crystals is extremely challenging. Here, the first chemical epitaxial growth of single crystal CH NH PbBr with controlled locations, morphologies, and orientations, using combined strategies of advanced microfabrication, homoepitaxy, and low temperature solution method is reported.

Nanostructuring Multilayer Hyperbolic Metamaterials for Ultrafast and Bright Green InGaN Quantum Wells.

Semiconductor quantum well (QW) light-emitting diodes (LEDs) have limited temporal modulation bandwidth of a few hundred MHz due to the long carrier recombination lifetime. Material doping and structure engineering typically leads to incremental change in the carrier recombination rate, whereas the plasmonic-based Purcell effect enables dramatic improvement for modulation frequency beyond the GHz limit. By stacking Ag-Si multilayers, the resulting hyperbolic metamaterials (HMMs) have shown tunability in the plasmonic density of states for enhancing light emission at various wavelengths.

Broadband Photonic Spin Hall Meta-Lens.

Meta-lens represents a promising solution for optical communications and information processing owing to its miniaturization capability and desirable optical properties. Here, spin Hall meta-lens is demonstrated to manipulate photonic spin-dependent splitting induced by spin-orbital interaction in transverse and longitudinal directions simultaneously at visible wavelengths, with low dispersion and more than 90% diffraction efficiency. The broadband dielectric spin Hall meta-lens is achieved by integrating two geometric phase lenses with different functionalities into one single dynamic phase lens, which manifests the ultracompact, portable, and polarization-dependent features.

Giant Kerr response of ultrathin gold films from quantum size effect.

With the size of plasmonic devices entering into the nanoscale region, the impact of quantum physics needs to be considered. In the past, the quantum size effect on linear material properties has been studied extensively. However, the nonlinear aspects have not been explored much so far.

Three-dimensional fluorescent microscopy via simultaneous illumination and detection at multiple planes.

The conventional optical microscope is an inherently two-dimensional (2D) imaging tool. The objective lens, eyepiece and image sensor are all designed to capture light emitted from a 2D 'object plane'. Existing technologies, such as confocal or light sheet fluorescence microscopy have to utilize mechanical scanning, a time-multiplexing process, to capture a 3D image.

Design of hybrid structure for fast and deep surface plasmon polariton modulation.

The electric and optical performance of different surface plasmon polariton (SPP) electric modulation structures have been investigated by comparing the response speed and modulation figures of merit (FoM). To overcome the capacitance limitation and improve the response speed, we proposed a novel silver-graphene-dielectric-graphene-semiconductor vertical structure. Semiconductor nano-waveguide is introduced to help reduce ohmic loss in silver waveguide and reflect the leaked optical field back, enhancing the modulation depth.

Electrical tuning of surface plasmon polariton propagation in graphene-nanowire hybrid structure.

We demonstrate a dynamic surface plasmonic modulation based on graphene-nanowire (grapheme-NW) hybrid structures in the visible light range. A static modulation depth of as high as 0.07 dB/μm has been achieved experimentally.