Perfect Light Absorption Research Articles

Angle-insensitive perfect light transmission and absorption in one-dimensional photonic crystal heterostructures

Abstract Prefect light transmission in metamaterials typically suffers a frequency shift as the incident angle of wave increase, limiting their applicability across wide angles. One-dimensional photonic crystal heterostructures, with elliptic-shaped equi-frequency contours, exhibit angle-insensitive properties. However, there remains an inevitable blue shift in the optical response as the incident angle increases. In this work, we present two photonic crystal heterostructures, one of which is composed of the optical phase-change material Sb2S3. By combining two heterostructures with distinct Zak phases, we achieve perfect light transmission. Specifically, as incident angle of wave increases, the transmission peak can be strictly maintained without a frequency shift by tuning the phase (refractive index) of Sb2S3. Moreover, by jointing the heterostructures with a thin silver film, we demonstrate a Tamm plasma polariton mode with angle-insensitive property. This mode can facilitate angle-tolerant light absorption. Our work provides an alternative way to designing high angle-tolerant and tunable devices.

Perfect absorption of violet light enabled by rotated Mie resonators

Perfect absorption of violet light enabled by rotated Mie resonators

Robust incoherent perfect absorption

A coherent perfect absorber is capable of completely absorbing input waves. However, the coherent perfect absorption severely depends on the superposition of the input waves, and the perfect absorption is sensitive to the disorder of the absorber. Thus, a robust incoherent perfect absorption, being insensitive to the superposition of input waves and the system disorder, is desirable for practical applications. Here, we demonstrate that the linearly independent destructive interference at the port connections removes the constraint on the coherent input. We propose an approach using the interplay between the loss and localization to form the incoherent perfect absorption. The resonant incidence from either port is completely absorbed. Furthermore, we utilize the lattice configuration supporting the flat band to demonstrate the disorder-immune incoherent perfect absorption. Our findings provide insight into the fundamentals and applications for the perfect absorption of light, microwaves, sound, mechanical waves, and beyond. Published by the American Physical Society 2024

Coherent perfect absorption of light by undoped graphene monolayer

We show theoretically that coherent perfect absorption (CPA) of light is possible by a graphene monolayer without doping. To achieve the CPA, undoped graphene is embedded inside a multilayer structure called mirror structure, which increases the effective impedance of the surrounding medium. The increased effective impedance allows the destructive interference of light outside the structure that induces an increased Joule heat generating perfect absorption of light by graphene. We find that the CPA is possible for any wavelength as long as the thickness of each layer of the structure is a quarter of the corresponding wavelength. By changing the incident wavelength, but keeping the thickness of each layer, we show that the optical absorption is sensitive to the change of the incident wavelength. Therefore, we can design a photo detector for a specific wavelength.

Vernier Ellipsometry Sensing with Ultralow Limit‐of‐Detection and Large Dynamic Range by Tuning of Zero‐Reflection Points

AbstractOptical sensors using zero‐reflection points (ZRPs) enable excellent sensitivity due to the accompanying phase singularities and the steepest slope of the reflectivity curve. Here, the collaborative manipulation of three ZRPs in a simple platform formed by a lithography‐free, metal‐dielectric‐metal structure with unsurpassed, experimentally demonstrated, limit of detection ≈2 × 10−8 refractive index unit is reported. The sensor relies on: i) strong coupling between p‐polarized surface plasmon polariton and photonic waveguide, leading to reflection suppression, Rabi splitting and phase singularities; ii) simultaneous implementation of two orthogonally polarized ZRPs, enabling spectral overlap of s‐polarized photonic modes (Rs) with the coupled p‐polarized resonances (Rp); and iii) ellipsometry‐based sensing where the s‐polarized ZRPs provide a stable reference to boost the sensor performance in terms of the amplitude ratio and phase difference of Rp and Rs thereby naturally forming a refinement measuring scale akin to a Vernier scale. Remarkably, the precise manipulation of ZRPs enables resetting the sensor to its optimal sensing point. The capability has been demonstrated for a biosensor of SARS‐CoV‐2 spike (S2) protein that can track the full functionalization process then reset to perform dose‐dependent detection of the S2 protein. This work provides a new strategy for the development of optical sensors and perfect light absorbers.

Perfect Solar Light Absorption and Efficient Photo-Thermal Generation

Perfect Solar Light Absorption and Efficient Photo-Thermal Generation

Giant bandwidth tailoring of perfect light absorbers: Empowered by quasibound states in the continuum

Giant bandwidth tailoring of perfect light absorbers: Empowered by quasibound states in the continuum

Bimetallic metasurface broadband perfect absorber for high-efficiency thermal photovoltaics

We theoretically propose and demonstrate that broadband polarization-insensitive perfect visible light absorption can be realized in a periodic bimetallic nanotriangle structure with a thick gold plate. The average absorption is 95.79% from 400 nm to 800 nm. The multiple localized surface plasmon resonances of the bimetallic nanostructure are the major contributions to this broadband perfect absorption in the visible region. Meanwhile, the physical mechanism of the broadband perfect absorption of the bimetallic nanostructure can be well interpreted by impedance matching theory. Moreover, the average photo-thermal conversion efficiency is up to 93% over a wide temperature range.

Facile construction of nanowires via etching process to increase heterostructure area for efficient photocatalysis

Semiconductor photocatalysts can eliminate organic pollutants completely, but the poor utilization of solar energy and rapid recombination of photogenerated electron-hole pairs have become a vital obstacle for their widespread application. Herein Si/TiO2 nanowire arrays with core–shell structures were fabricated by metal-assisted chemical etching and atomic-layered deposition. The physical properties and photocatalytic performance of the specimens were tested and compared with pristine Si nanowire arrays. The specimens showed perfect light absorption. The photoluminescence was generally depressed by the shell layer, and the photocurrent and photocatalytic efficiency of Si/TiO2 were improved by 297 and 2 times respectively in contrast to Si. The magnitude of the photocurrent and photocatalytic activity could be modulated by the etching period, in which an ideal etching time of 2 h produced the highest photocatalytic performance. The high efficient photocatalysis of the heterostructure was well illustrated by the Z-scheme band alignment and large specific surface area.

Nanoscale modeling of dynamically tunable planar optical absorbers utilizing InAs and InSb in metal-oxide-semiconductor–metal configurations

The attainment of dynamic tunability in spectrally selective optical absorption has been a longstanding objective in modern optics. Typically, Fabry–Perot resonators comprising metal and semiconductor thin films have been employed for spectrally selective light absorption. In such resonators, the resonance wavelength can be altered via structural modifications. The research has progressed further with the advent of specialized patterning of thin films and the utilization of metasurfaces. Nonetheless, achieving dynamic tuning of the absorption wavelength without altering the geometry of the thin film or without resorting to lithographic fabrication still poses a challenge. In this study, the incorporation of a metal-oxide-semiconductor (MOS) architecture into the Fabry–Perot nanocavity is shown to yield dynamic spectral tuning in a perfect narrowband light absorber within the visible range. Such spectral tuning is achieved using n-type-doped indium antimonide and n-type-doped indium arsenide as semiconductors in a MOS-type structure. These semiconductors offer significant tuning of their optical properties via electrically induced carrier accumulation. The planar structure of the absorber models presented facilitates simple thin-film fabrication. With judicious material selection and appropriate bias voltage, a spectral shift of 47 nm can be achieved within the visible range, thus producing a discernible color change.

Plasmonic Nanoneedle Arrays with Enhanced Hot Electron Photodetection for Near‐IR Imaging

AbstractHot electron photodetection based on metallic nanostructures is attracting significant attention due to its potential to overcome the limitation of the traditional semiconductor bandgap. To enable efficient hot electron photodetection for practical applications, it is necessary to achieve broadband and perfect light absorption within extremely thin plasmonic nanostructures using cost‐effective fabrication techniques. In this study, an ultrahigh optical absorption (up to 97.3% in average across the spectral range of 1200−2400 nm) is demonstrated in the ultrathin plasmonic nanoneedle arrays (NNs) with thickness of 10 nm, based on an all‐wet metal‐assisted chemical etching process. The efficient hot electron generation, transport, and injection at the nanoscale apex of the nanoneedles facilitate the photodetector to achieve a record low noise equivalent power (NEP) of 4.4 × 10−12 W Hz−0.5 at the wavelength of 1300 nm. The hot‐electron generation and injection process are elucidated through a transport model based on a Monte Carlo approach, which quantitatively matches the experimental data. The photodetector is further integrated into a light imaging system, as a demonstration of the exceptional imaging capabilities at the near‐IR regime. The study presents a lithography‐free, scalable, and cost‐effective approach to enhance hot electron photodetection, with promising prospects for future imaging systems.

High efficiency 2D/0D/3D Z-scheme rGO@g-C3N4/TiO2 nanobelt-tubes heterojunction for tetracycline degradation under visible light: Electrochemical synthesis, performance, and mechanisms

Photocatalytic water treatment is drawing attention for the abatement of organic contaminants with solar energy. Herein, an immobilized rGO@g-C3N4/TiO2 nanobelt-tubes (GCTs) heterojunction photocatalyst coating on titanium plates was fabricated via implementable anodizing and electrodeposition technology and systematically investigated their morphologies and photoelectrochemical properties. The GCTs held the unique 2D/0D/3D sandwich-like nanobelt-tubes arichitecture, perfect visible light absorption (400–500 nm) performance, and high charge transfer capacity, which contributed to the enhancement photocatalytic activity and recyclability for tetracycline degradation, particularly under visible light irradiations. The optimal GCTs photocatalyst showed higher photocatalytic degradation efficiency (81.46 %) compared to pure TiO2 (62.77 %). Photocatalytic activity of GCTs only suffered a small decrease in tetracycline degradation efficiency after 6 operation cycles, from 81.46 % to 76.06 %. Z-scheme interfacial charge transfer mechanism operates for the GCTs during photocatalytic degradation, as authenticated by in situ X-ray photoelectron spectroscopy, quenching tests and electron spin resonance spectra. The tetracycline degradation efficiency was enhanced under alkaline conditions from 35.17 % to 71.11 %. The degradation pathways were also clarified based on HPLC/MS analysis, and the overall toxicity of tetracycline was effectively mitigated after photodegradation. The GCTs photocatalyst provide an effective strategy for the photocatalytic degradation of antibiotics in natural waters.

Substrate-mediated plasmon hybridization toward high-performance light trapping.

High-performance light trapping in metamaterials and metasurfaces offers prospects for the integration of multifunctional photonic components at subwavelength scales. However, constructing these nanodevices with reduced optical losses remains an open challenge in nanophotonics. Herein, we design and fabricate aluminum-shell-dielectric gratings by integrating low-loss aluminum materials with metal-dielectric-metal designs for high-performance light trapping featuring nearly perfect light absorption with broadband and large angular tuning ranges. The mechanism governing these phenomena is identified as the occurrence of substrate-mediated plasmon hybridization that allows energy trapping and redistribution in engineered substrates. Furthermore, we strive to develop an ultrasensitive nonlinear optical method, namely, plasmon-enhanced second-harmonic generation (PESHG), to quantify the energy transfer from metal to dielectric components. Our studies may provide a mechanism for expanding the potential of aluminum-based systems in practical applications.

Perfect light absorber with a PT phase transition via coupled topological interface states

Recently, the concepts of parity–time (PT) symmetry and band topology have inspired many novel ideas for light manipulation in their respective directions. Here we propose and demonstrate a perfect light absorber with a PT phase transition via coupled topological interface states (TISs), which combines the two concepts in a one-dimensional photonic crystal heterostructure. By fine tuning the coupling between TISs, the PT phase transition is revealed by the evolution of absorption spectra in both ideal and non-ideal PT symmetry cases. Especially, in the ideal case, a perfect light absorber at an exceptional point with unidirectional invisibility is numerically obtained. In the non-ideal case, a perfect light absorber in a broken phase is experimentally realized, which verifies the possibility of tailoring non-Hermiticity by engineering the coupling. Our work paves the way for novel effects and functional devices from the exceptional point of coupled TISs, such as a unidirectional light absorber and exceptional-point sensor.

Surface plasmon polariton assisted near perfect light absorption from corrugated metal–insulator–metal structure exploiting lossy metal films

We propose and demonstrate a lithography-free self-assembled corrugated Cr/TiO2/Cr metal–insulator–metal (Cr-cMIM) structure on silica opal substrates for broadband near perfect light absorption applications. Our optimal Cr-cMIM structure have reached a spectral average absorption rate above 98% over the visible wavelength range. We carried out numerical calculations to simulate the interaction between the incident light and the Cr-cMIM structure. The simulated absorption spectra qualitatively reproduced the experimental results. Detailed analysis of the simulation results indicates that the corrugation of the Cr layers successfully couples the incident light with the localized surface plasmon polariton. The incorporation of the surface plasmonic excitation and the intrinsic ohmic dissipation of the Cr layers results in the broadband near perfect light absorption over the visible wavelength range.

Working Mechanism and Progress of Electromagnetic Metamaterial Perfect Absorber

Electromagnetic metamaterials are artificial subwavelength composites with periodic structures, which can interact strongly with the incident light to achieve effective control of the light field. Metamaterial absorbers can achieve nearly 100% perfect absorption of incident light at a specific frequency, so they are widely used in sensors, optical switches, communication, and other fields. Based on the development history of metamaterials, this paper discusses the research background and significance of metamaterial perfect absorbers. Some perfect absorption mechanisms, such as impedance matching and coherent perfect absorption, are discussed. According to the functional division, the narrowband, dual frequency, multi-frequency, broadband, and tunable metamaterial perfect absorbers are briefly described.

Metallic Plasmonic Nanostructure Arrays for Enhanced Solar Photocatalysis

AbstractPlasmon‐enhanced photocatalysis has emerged as a promising technology for solar‐to‐chemical energy conversion. Compared to isolated or disordered metal nanostructures, by controlling the morphology, composition, size, spacing, and dispersion of individual nanocomponents, plasmonic nanostructure arrays with coupling architectures yield strong broadband light‐harvesting capability, efficient charge transfer, enhanced local electromagnetic fields, and large contact interfaces. Although metallic nanostructure arrays are extensively studied for various applications, such as refractive index sensing, surface‐enhanced spectroscopy, plasmon‐enhanced luminescence, plasmon nanolasing, and perfect light absorption, the connection between surface plasmon resonance and enhanced photocatalysis remains relatively unexplored. In this study, an overview of plasmonic nanostructure arrays over a broad range, from 0D to 3D, for efficient photocatalysis is presented. By reviewing the fundamental mechanisms, recent applications, and latest developments of plasmonic nanostructure arrays in solar‐driven chemical conversion, this study reports on the latest guidance toward the integration of plasmonic nanostructures for functional devices in the fields of plasmonic, photonics, photodetection, and solar‐energy harvesting.

VO2 Tungsten Doped Film IR Perfect Absorber

We investigated infrared reflectivity of undoped and Tungsten (W) doped Vanadium dioxide (VO2) films at varying temperatures. Undoped VO2 exhibited a clear phase transition at 100°C, achieving near 0% reflectivity, or perfect light absorption. As W doping concentration increased, the phase-transition temperature decreased, maintaining the zero-reflectivity condition. Only a 0.75% W doping enabled room temperature perfect absorption without heating the film.

Ultra-thin deep ultraviolet perfect absorber using an Al/TiO2/AlN system.

An ultra-thin perfect absorber for deep ultraviolet light was realized using an Al/TiO2/AlN system. The TiO2 thickness was optimized using the Fresnel phasor diagram in complex space to achieve perfect light absorption. As a result of the calculation almost perfect absorption into the TiO2 film was found, despite the film being much thinner than the wavelength. An optimized Al/TiO2/AlN system was fabricated, and an average absorption greater than 97% was experimentally demonstrated at wavelengths of approximately 255-280 nm at normal light incidence. Our structure does not require nanopatterning processes, and this is advantageous for low-cost and large-area manufacturing.

Strong and Omnidirectional Light Absorption from Ultraviolet to Near‐Infrared Using GST Metasurface

AbstractFor the perfect light absorber, it has been a huge challenge to simultaneously realize ultra‐broadband and strong absorption of unpolarized light over a large angular range, though various materials and designs have been tried. The emergence of optical metasurface with powerful light field regulation ability provides a promising new strategy for achieving perfect absorbers. Here, a Ge2Sb2Te5 (GST)‐based metasurface with an average 92.5%/94.7% (experiment/simulation) absorptivity of unpolarized light, covering an ultra‐broadband from ultraviolet to near‐infrared region is designed and demonstrated. This GST‐based metasurface consists of double‐layer GST interspaced by SiO2 layer, and both field localizations in the top patterned GST layer and intrinsic loss of the bottom patternless GST layer together contribute to this broadband absorption over wide incident angles up to 70°. Strong absorbing ability, large angular responses, and feasibly scalable fabrication for such a perfect GST‐based metasurface absorber offer more promising application opportunities in integrated optoelectronic devices.