Versatile Light Research Articles

Directionally Asymmetric in Orbital Angular Momentum Generation Using Single‐Layer Dielectric Janus Metasurfaces

AbstractJanus metasurfaces, offering versatile light manipulation contingent on incident direction, are explored across microwave to mid‐infrared spectra. Nonetheless, prior designs often resort to spatial multiplexing or vertical stacking, entailing complex fabrication. Metallic Janus metasurfaces, owing to material properties, suffer notable Ohmic losses in the visible spectrum. In this study, Single‐layer TiO2‐based Janus metasurfaces with arbitrary polarization control is experimentally demonstrated, exhibiting directionally asymmetric functionalities in spin and orbital angular momentum (OAM). A novel Jones matrix formulation tailored for Janus metasurfaces is presented, enabling efficient generation of two asymmetric, high‐purity OAM states of vortex beams at wavelength of 532 nm, contingent on incidence direction. This innovation facilitates compact and versatile phase manipulation, encompassing applications such as lasers and optical combiners, thereby expanding its utility across diverse domains.

STEM Developments: A Versatile Light Injector/Collector, Fast 4D-STEM, and High Energy Resolution EELS without Compromising Beam Current

STEM Developments: A Versatile Light Injector/Collector, Fast 4D-STEM, and High Energy Resolution EELS without Compromising Beam Current

Anisotropy-free arrayed waveguide gratings on X-cut thin film lithium niobate platform of in-plane anisotropy

Arrayed waveguide grating is a versatile and scalable integrated light dispersion device, which has been widely adopted in various applications, including, optical communications and optical sensing. Recently, thin-film lithium niobate emerges as a promising photonic integration platform, due to its ability of shrinking largely the size of typical lithium niobate based optical devices. This would also enable multifunctional photonic integrated chips on a single lithium niobate substrate. However, due to the intrinsic anisotropy of the material, to build an arrayed waveguide grating on X-cut thin-film lithium niobate has never been successful. Here, a universal strategy to design anisotropy-free dispersive components on a uniaxial in-plane anisotropic photonic integration platform is introduced for the first time. This leads to the first implementation of arrayed waveguide gratings on X-cut thin-film lithium niobate with various configurations and high-performances. The best insertion loss of 2.4 dB and crosstalk of −24.1 dB is obtained for the fabricated arrayed waveguide grating devices. Applications of such arrayed waveguide gratings as a wavelength router and in a wavelength-division multiplexed optical transmission system are also demonstrated.

Bhangarh Fort : India of to All Scary Castle

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Mid-infrared dual-comb spectroscopy with quantum cascade lasers

Since its invention in 1994, the quantum cascade laser (QCL) has emerged as a versatile light source of wavelength 4–12 µm, covering most of the mid- and long-wavelength infrared spectral ranges. Its application range has widened even further since frequency comb operation and its use as a light source for dual-comb spectroscopy (DCS) was demonstrated. In this tutorial, we introduce the unique properties of QCL frequency combs, such as high optical power, multi-GHz repetition rate, and narrow optical linewidths. Implemented in a dual-comb spectroscopy setup, this allows for broadband, low-noise measurements of strongly absorbing samples with sub-microsecond time resolution, and spectral resolution better than 10−3 cm−1/30 MHz. The advantages of QCL DCS will be discussed in the context of its broad range of applications. The high optical power (both total and per comb tooth) is leveraged for measurements in aqueous solution or at large stand-off distances. Microsecond temporal resolution measurements address the demand for probing rapid protein dynamics and combustion diagnostics. MHz-level spectral resolution, in turn, facilitates accurate line parameter studies in low pressure and cold molecular gases. Future development directions of the technology are discussed, including sub-microsecond response DCS, instrument miniaturization, or its expansion toward THz frequencies. Overall, the tutorial aims at giving a broad introduction to QCL DCS and its applications.

Silver zirconate: A versatile visible light harvesting photocatalyst for oxygen evolution, PMS activation, and bactericidal activity

Herein, we have synthesized silver zirconate using a co-precipitation method at room temperature. The synthesized Ag2ZrO3 (SZ) was then subjected to calcination at different temperatures (300 °C, 500 °C, and 700 °C). The synthesized Ag2ZrO3 materials were evaluated for their photocatalytic oxygen evolution, activation of peroxymonosulfate (PMS) ions, and antibacterial activity under visible light irradiation. Among the different samples, the SZ sample (Ag2ZrO3 synthesized at room temperature) exhibited the highest photocatalytic oxygen evolution rate (2175.02 μmolg-1h−1). This enhanced performance can be attributed to the higher surface area of SZ compared to the other samples. Furthermore, all four samples were tested for the photoactivation of peroxymonosulfate (PMS) ions to assess their ability for the decontamination of organic pollutant. The SZ photocatalyst demonstrated complete degradation (100 %) of RhB dye (2.1 × 10-5 M) within 120 min of visible light irradiation in the presence of PMS. In contrast, without PMS, only 54.33 % degradation of RhB was recorded in 300 min. This result indicates that SZ effectively activates PMS ions for the degradation of organic pollutants. Additionally, SZ exhibited excellent bactericidal activity against E. coli and S. aureus bacteria, both in the dark and in the presence of visible light. The findings demonstrate the multifunctional properties of Ag2ZrO3, making it suitable for a wide range of environmental remediation applications.

A Photocatalytic Approach for the Synthesis of L‐Shape Bicyclic NHC Ligands

AbstractL‐shape N‐Heterocyclic Carbenes (NHCs) based on the imidazo[1,5‐a]pyridine (ImPy) scaffold have recently gained considerable interest as the true carbene ligand analogues of the popular dialkylbiarylphosphines, better known as Buchwald phosphines. Nevertheless, the substitution pattern of ImPy ligands is still rather limited due to synthetic access issues. We report herein an efficient and versatile visible light photocatalytic strategy to access L‐shape bifunctional ImPy ligands laterally‐functionalized by a phenol group. Mechanistic investigations supported by density functional theory (DFT) reveal that the excited state of the iridium photocatalyst undergoes either a reductive quenching (SET process) or an energy‐transfer quenching (EnT process) depending on the nature of the counterion of the 5‐bromoimidazo[1,5‐a]pyridinium substrate salt. Moreover, the bifunctional character of these new family of L‐shape ImPy ligands is demonstrated by the preparation of a gold(I) complex exhibiting a free OH function capable of intermolecular hydrogen bonding. This work highlights the advantage of visible light photocatalysis in the synthesis of advanced NHC ligand structures, a strategy that has not yet been considered despite its potential benefits in terms of versatility, diversity and practicability.

Longitudinal polarization manipulation based on all-dielectric terahertz metasurfaces

Polarization modulation of electromagnetic waves plays an important role in the field of optics and optoelectronics. Current polarization optics are typically limited to the modulation in a single transverse plane. However, manipulating polarization along the longitudinal direction is also important for full-space polarization modulation. Here, we propose two kinds of all-dielectric terahertz metasurfaces for longitudinally spatial polarization manipulation. The metasurfaces are capable of controlling polarization along the propagation path, namely: i) a longitudinal bifocal metalens with different polarization states at each focal point, and ii) a versatile metalens can simultaneously generate a uniformly polarized focused beam and a vector beam with varying polarization along the propagation path. Furthermore, the measurement of the dielectric thickness is demonstrated based on the polarization modulation feature of the metalens. The proposed metasurfaces allow for effective polarization state alteration along the propagation path, exhibiting significant potential for applications in versatile light–matter interactions, optical communications, and quantum optics.

Multi-wavelength and broadband AlGaN-based LED for versatile and artificial UV light source

This study focuses on modeling and analyzing a multi-wavelength (MW) ultraviolet light-emitting diode (UV LED) equipped with grading transition layers, which holds potential as a versatile and artificial UV light source. Commencing with the exploration of simple dual and triple-wavelength UV LEDs, we delve into the device mechanism, including the role of the grading transition layer and the control of emission intensity ratios. The grading transition layer connects modules with different emission wavelengths, effectively enhancing hole injection by diminishing the effective hole barrier and providing three-dimensional hole gas (3DHG). Besides, the emission intensity ratio of different modules is modulated through electron overflow, which is finely and coarsely controlled respectively by altering the quantum well number and the Al composition of electron controlling layers (ECLs). Modulating the ECL composition and quantum well number has good unilaterality facilitated by using grading transition layers, promoting a lower overall design complexity. Band diagrams, current dynamics, and carrier concentration distribution are analyzed to uncover various device mechanisms. After investigating dual-wavelength and triple-wavelength LEDs, a broadband UV LED is designed and demonstrated through the numerical method. The LED incorporates five emission modules, and each module has a similar emission intensity, contributing to a near 100 nm width UV spectrum. We expect this work lays the foundation for MW and broadband UV LED designs, fostering advancements in the AlGaN-based UV LED community.

Diya – A universal light illumination platform for multiwell plate cultures

Recent progress in protein engineering has established optogenetics as one of the leading external non-invasive stimulation strategies, with many optogenetic tools being designed for invivo operation. Characterization and optimization of these tools require a high-throughput and versatile light delivery system targeting micro-titer culture volumes. Here, we present a universal light illumination platform- Diya, compatible with a wide range of cell culture plates and dishes. Diya hosts specially designed features ensuring active thermal management, homogeneous illumination, and minimal light bleedthrough. It offers light induction programming via a user-friendly custom-designed GUI. Through extensive characterization experiments with multiple optogenetic tools in diverse model organisms (bacteria, yeast, and human cell lines), we show that Diya maintains viable conditions for cell cultures undergoing light induction. Finally, we demonstrate an optogenetic strategy for invivo biomolecular controller operation. With a custom-designed antithetic integral feedback circuit, we exhibit robust perfect adaptation and light-controlled set-point variation using Diya.

Research on Light Extraction of GaN-based LED with Surface/Interface Coarsening

Light-emitting diodes (LEDs) are a highly versatile light source that have been widely employed in various fields. In order to maximize its quantum efficiency, it is essential to boost the efficiency of light extraction. Internal photon reflection can have a distinct negative impact on the luminous output power of GaN-based LEDs, which can be addressed by surface and interface texturing of different LED layers. This article discusses the mechanisms of light extraction losses in GaN-based LEDs and summarizes various surface and interface coarsening techniques proposed for improving the light extraction rate, including a range of physical and chemical etching methods.

Narrowing the bandgaps of thiazolo[5,4-d]thiazole-bridged conjugated microporous polymers to capture green light for selective oxidation of amines

Conjugated microporous polymers (CMPs) have evloved into versatile visible light photocatalysts. Narrowing the bandgaps of CMPs could capture more visible light without shifting the suitable position with an established electron acceptor like thiazolo[5,4-d]thiazole (TzTz). Here, benzene-1,3,5-tricarbaldehyde (Bz-CHO) and benzo[1,2-b:3,4-b':5,6-b'']trithiophene-2,5,8-tricarbaldehyde (BTT-CHO) are adopted to undergo condensation with dithiooxamide, preparing two TzTz-bridged CMPs, namely TzTz-Bz and TzTz-BTT. Thereby, TzTz-BTT could capture visible light more substantially than TzTz-Bz due to narrowing the bandgap. Endowed by TzTz, both TzTz-BTT and TzTz-Bz possess similar positions for the activation of O2 and can drive the subsequent formation of imines. However, TzTz-BTT, with a narrower bandgap, could capture more green light to drive the electron and proton transfer for the selective formation of imines with higher conversions than TzTz-Bz. This work suggests that CMPs can be equipped with extensive visible light absorption for photocatalytic selective oxidations.

Light Fueled Manipulation of Bubble Motion Against Buoyancy via Photosensitive Substrate

AbstractFlexibly and precisely controlling bubbles is of paramount significance for biological and chemical analysis, reaction engineering, etc. However, the buoyancy force acting on bubbles is significant, making it difficult to precisely manipulate bubbles. Particularly, controlling the anti‐buoyancy motion of bubbles remains a fundamental challenge. Herein, a versatile light strategy for manipulating the anti‐buoyancy motion of bubbles via a photosensitive substrate is developed. Upon focused laser beam irradiation, an intense Marangoni effect associated with non‐uniform temperature distribution is induced underneath the bubble. The created excess Laplace pressure drives the bubble to move against the buoyancy force downward to the focused‐laser‐acted region, manifesting an excellent phototaxis motion. Theoretical analysis demonstrates that the Marangoni effect is responsible for actuating the anti‐buoyancy motion of a bubble. With this light strategy, the bubble collection, transportation, and on‐demand release can be flexibly implemented. Moreover, the phototaxis motion of bubbles inspires a manipulation protocol via the integration of 3D‐structured design of photosensitive substrate. This light strategy for manipulating bubbles not only possesses sufficiently high accuracy and quick response, but also circumvents the limitation of the liquid volatility and multi‐dimensional motion, which provides new ideas for rational control of bubble behaviors.

First principles study of optical properties of Ni- and Pd-doped TiO2 as visible light catalyst

Doping TiO2 with noble metals, transition metals, cations, anions have yielded very promising results in enhancing photocatalytic activity of TiO2 in the visible region and its role in generating alternate forms of energy. Noble metals in general can effectively slow down carrier recombination. However, the study of Pd and Ni as dopant can lead to a reliable and versatile TiO2-modified photocatalyst. In this paper, we explore the optical properties of Pd- and Ni-doped TiO2 by doping with 4.17% Ni and Pd dopant concentrations. The optical properties prove that Ni-doped TiO2 can absorb well in the visible region with an absorption coefficient of 1 × 105 cm−1. Hence, Ni-doped TiO2 can successfully alter the electronic and optical properties of TiO2 for favorable future applications. In the visible region, absorption coefficient of Pd-doped TiO2 supercell is around 1.2 × 105 cm−1 which is comparatively greater than that of pure TiO2 confirming its utility as a versatile and viable visible light photocatalyst. The other optical properties like reflectivity, refractivity, extinction coefficient and electron energy loss spectrum have also been studied.

Evolution of Wigner-distribution-function oblique Airy-Airy vortex wavepackets in a dispersive chiral medium

This paper introduces a distinctive perspective to describe and construct a new type of spatiotemporal optical field. Being different from the previous traditional wave packet obtained from the (3+1) D Schrödinger equation in the real space, the newly proposed nonclassical oblique Airy-Airy vortex (OAAV) wave packet located in the phase and momentum space is constructed based on the Wigner-distribution-function (Wdf) method. The spatiotemporal dynamics of the Wigner-distribution-function oblique Airy-Airy vortex (WdfOAAV) wave packet propagating in a dispersive chiral medium (DCM) are investigated from various aspects, including the targeted wave packet's nonclassicality, propagation properties, angular momentum density, and lateral optical force. It is found that the medium's chirality would remove the degeneracy of the propagation velocities in momentum space, which would result in the accelerated and decelerated wave packets propagating without diffusion within several Rayleigh lengths. The WdfOAAV wave packet associates the time-space optical field in the phase and momentum space with that in the real space, and offers the essential information about the joint spatial position and phase/momentum distribution in arbitrary real-space coordinates. Results obtained here might open a new perspective for the construction of a nonclassical spatiotemporal optical field and be applied in particle manipulation and versatile light bullets.

Gap‐Surface Plasmon‐Enhanced Photoluminescence of InSe

2D materials, with distinct characteristics compared to their conventional bulk counterparts, have been a popular topic in various optoelectronic research fields. Herein, indium selenide (InSe), a monochalcogenide van der Waals layered semiconductor, which has been studied due to its thickness dependent optical characteristics is explored. For InSe to be used as a versatile light source, enhancing the emission of InSe is required. Here, enhanced photoluminescence (PL) from multi‐layer InSe is demonstrated using a gap plasmon induced between Ag nanocube dimer and an Au substrate. Such plasmonic structures support multiple resonances, one of those overlapping with InSe's band edge PL emission. The calculated Purcell factor shows a 200‐fold increase on the short edge of nanocube dimers. Experimentally, PL enhancement of 6‐fold is demonstrated at room temperature. In addition, a method for determining the thickness of 2D materials via dark‐field spectroscopy using white light illumination is shown. This study paves the way for the incorporation of 2D InSe into nanophotonic structures.

Thermometry of liquid water through slow light imaging spectroscopy.

This work presents the first, to the best of our knowledge, experimental demonstration of slow light imaging spectroscopy for thermometry of liquid water. This novel technique for measuring temperature relies on detecting the spectral shift of Brillouin peaks in water using the temporal delay through a cell containing an atomic vapor. Stand-off sensing capabilities are achieved by time-domain measurements of Brillouin scattering tuned to be near a rubidium atomic resonance and passed through a cell filled with rubidium vapor. An injection seeded optical parametric oscillator (OPO) is demonstrated to be a versatile light source for slow light imaging spectroscopy applications. The narrow OPO pulse spectrum allows for a precise profiling of slow light features of rubidium and accurate tracking of the temperature dependence of Brillouin scattering spectral shift. A comparison between the experimental data and numerical simulation over a temperature range of 20 to 99 degrees Celsius shows a good agreement for both qualitative and quantitative results.

Quantum arbitrary waveform generator.

Controlling the temporal waveform of light is the key to a versatile light source in classical and quantum electronics. Although pulse shaping of classical light is mature and has been used in various fields, more advanced applications would be realized by a light source that generates arbitrary quantum light with arbitrary temporal waveforms. We call such a device a quantum arbitrary waveform generator (Q-AWG). The Q-AWG must be able to handle various quantum states of light, which are fragile. Thus, the Q-AWG requires a radically different methodology from classical pulse shaping. Here, we invent an architecture of Q-AWGs that can operate semi-deterministically at a repetition rate over gigahertz in principle. We demonstrate its core technology via generating highly nonclassical states with temporal waveforms that have never been realized before. This result would lead to powerful quantum technologies based on Q-AWGs such as practical optical quantum computing.

Light manipulation by dual channel storage in ultra-cold Rydberg medium

We investigate the light propagation dynamics in ultra-cold Rydberg medium with inverted-Y configuration based on the superatom theory. It is viable to store light information in two types of atomic spin coherence (trivial spin coherence and Rydberg spin coherence), which makes the system a prospective platform for versatile light manipulation. A normal feature is to realize efficient light storage with simultaneous resonant control fields applied. An intriguing feature is to split light into two beams with different intensities and statistical properties if the control fields are applied separately. The beam of light retrieved from the Rydberg spin coherence is severely attenuated and shows anti-bunching character accompanied by the cooperative optical nonlinearity. Moreover, generation and manipulation of beating signal are achievable by applying the non-resonant control fields.

M13 bacteriophage as biometric component for orderly assembly of dynamic light scattering immunosensor

The ordered assembly of nanostructure is an effective strategy used to manipulate the hydrodynamic diameter (DH) of nanoparticles. Herein, a versatile dynamic light scattering (DLS) immunosensing platform is presented to sensitively detect small molecules and biomacromolecules by using the M13 phage as the building module to order the assembly of gold nanoflowers and gold-coated magnetic nanoparticles, respectively. After the directional assembly of M13 phage, the DH of the probes was significantly increased due to its larger filamentous structure, thus improving the detection sensitivity of the DLS immunosensor. The designed M13 assembled DLS immunosensor with competitive and sandwich formats showed high sensitivities for ochratoxin A and alpha-fetoprotein in real corn and undiluted serum samples, with the detection limits of 1.37 and 57 pg/mL, respectively. These values are approximately 15.8 and 164.9 times lower than those of traditional phage-based enzyme-linked immunosorbent assays. Collectively, this work provides a promising strategy to manipulate the DH of nanoparticles by highly evolved biomaterials such as engineered M13 phages and opens upon a new direction for developing DLS immunosensors to detect various targets by the fusion expression of special peptide or nanobody on the pIII or pVIII protein of M13 phage.