Transparency Effect Research Articles

Transfunctional Optical Thin Films via Bioinspired Engineering.

Advanced multifunctional optical films or substrates have continued to develop as essential components in the diverse optical industry. Several functions, including high transparency, self-cleaning ability, structural color, flexibility, and durability, are required to obtain versatile and practical optical films. Herein, we introduce a cicada-wing-inspired transfunctional optical thin film (CITOTF) with nanostructures on both surface nanostructures inspired by the cicada-wings. CITOTFs made of perfluoropolyether (PFPE), which has a low refractive index, low surface energy, and high robustness as a substrate material, are obtained by a well-designed sandwich lithography method. We fabricated two types of CITOTFs depending on the size (300 and 1000 nm) of the surface nanostructure. 300-CITOTF and 1000-CITOTF exhibit high transparency and structural color effects, respectively. Both samples demonstrate self-cleaning ability, flexibility, and long-term stability. The bioinspired transfunctional optical films developed in this study can be used in various optical applications.

Three-dimensional metamaterial for reconfigurable multi-band electromagnetically induced transparency based on VO2

Conventional 2D planar metamaterials struggle to achieve multi-band electromagnetically induced transparency (EIT) effects due to structural constraints. This paper proposes what we believe to be a novel three-dimensional (3D) metamaterial consisting of a vertical split-ring resonator with vanadium dioxide (VO2) islands at the openings. Based on VO2’s reversible phase transition capabilities, the designed metamaterial has excellent reconfigurability for multi-band EIT effects. When the surface temperature is at room temperature, VO2 exhibits an insulating state. The near-field coupling between bright and dark modes leads to a triple-band EIT effect at 1.72, 1.82, and 1.91 THz, characterized by multi-band, low-loss, and narrowband filtering. In contrast, when the temperature exceeds 68°C, VO2 transitions to its metallic state, resulting in a single transmission window with favorable slow light characteristics. Compared to traditional EIT metamaterials, our work realizes multi-band modulation and switchable operating modes, enhancing flexibility and adaptability. The excellent performance indicates its suitability for various applications, including multi-channel sensors, switchable absorptions, enhancing coupling and slow light devices, etc.

CrystalNet: Texture‐Aware Neural Refraction Baking for Global Illumination

AbstractNeural rendering bakes global illumination and other computationally costly effects into the weights of a neural network, allowing to efficiently synthesize photorealistic images without relying on path tracing. In neural rendering approaches, G‐buffers obtained from rasterization through direct rendering provide information regarding the scene such as position, normal, and textures to the neural network, achieving accurate and stable rendering quality in real‐time. However, due to the use of G‐buffers, existing methods struggle to accurately render transparency and refraction effects, as G‐buffers do not capture any ray information from multiple light ray bounces. This limitation results in blurriness, distortions, and loss of detail in rendered images that contain transparency and refraction, and is particularly notable in scenes with refracted objects that have high‐frequency textures. In this work, we propose a neural network architecture to encode critical rendering information, including texture coordinates from refracted rays, and enable reconstruction of high‐frequency textures in areas with refraction. Our approach is able to achieve accurate refraction rendering in challenging scenes with a diversity of overlapping transparent objects. Experimental results demonstrate that our method can interactively render high quality refraction effects with global illumination, unlike existing neural rendering approaches. Our code can be found at https://github.com/ziyangz5/CrystalNet

Nonlinear enhanced mass sensor based on optomechanical system

Abstract A high-precision and tunable mass detection scheme based on a double-oscillator optomechanical system is proposed. By designating one of the oscillators as the detection port, tiny mass signals can be probed through the frequency shift of the output spectrum, utilizing the system's optomechanically induced transparency (OMIT) effect. By solving the output of the optical mode, we demonstrate that the system exhibits two OMIT windows due to the double oscillator coupling, with one window being strongly dependent on the mass to be detected. Characterizing the spectrum around this window enables high magnification and precise detection of the input signal under nonlinear parameter conditions. Additionally, our scheme shows resilience to environmental temperature variations and drive strength perturbations.

Graphene modulator and 2-bit encoder based on plasma induced transparency effect

Within this study, a periodic metasurface structure made up of two graphene strips, two fan-shaped graphene and a square ring graphene with notches is introduced to achieve plasma-induced transparency (PIT). The PIT effect is analyzed utilizing the Lorentz oscillatory coupling model, and it has been discovered that the theoretical values closely match the simulated values. The role of the Fermi level adjustments in graphene on the PIT effect was examined, and the PIT window was dynamically modified as the Fermi level changed, which was used to realize a 2-bit graphene encoder at 5.78 THz and 7.18 THz. The encoder boasts a greatest modulation depth of 80.9 % and exhibits a minimal insertion loss of 0.17 dB. By controlling the polarization direction of the incident photoelectric field, a high performance dual-channel switching modulator is successfully realized. Moreover, by increasing carrier mobility, the depth of modulation for the modulator at 11.22 THz is increased from 97.5 % to 99.5 %, and the insertion loss has dropped from 0.075 dB to 0.06 dB. In addition, the structure has superior sensing properties and slow light properties, featuring a sensitivity reaching up to 1.07 THz/RIU and a maximum group index of 293. The outcomes of our study contribute novel insights for the advancement of modulator, encoder, sensor technology and slow-light devices.

Neutral donors confined in semiconductor coupled quantum dot-rings: Position-dependent properties and optical transparency phenomenon

Electronic properties of a neutral donor confined in a GaAs coupled quantum dot-ring covered by a Al0.3Ga0.7As matrix were calculated using the finite element method under the effective mass and the envelope function approximations. The proposed model is set up to fit a realistic coupled quantum dot-ring geometry revealed by atomic force microscopy images. The results show that the energy levels and the transition energies in the presence of an electric field strongly depend on the donor center’s angular position. Furthermore, the total optical absorption coefficient is calculated within the two-level approximation and the matrix density formalism. The absorption spectrum shows that the system can be tuned between 5 and 30meV. Also, an optical transparency effect for different configurations characterized by specific donor center’s angular positions and electric field values is seen. Finally, a novel redshift is observed when the sample temperature increases.

Optimized graphene metamaterial for dual plasmon-induced transparency in terahertz band with multifunctional applications

Abstract This paper proposes a patterned graphene periodic metamaterial structure, optimized using an improved genetic algorithm to adjust the position and size of each graphene strip, thereby achieving dual plasmon-induced transparency (PIT) effects in the terahertz band, resulting in extraordinary multifunctionality. The finite difference time domain method is employed to obtain the transmission spectrum, and coupled mode theory is used for theoretical analysis and verification of the dual-PIT effect. The structure exhibits multifunctionality: when used as a photoelectric switch, it achieves a modulation depth of up to 99.04% with an insertion loss as low as 0.16 dB by tuning the Fermi level. Additionally, the structure demonstrates excellent sensing performance, with a maximum sensitivity and figure of merit reaching 0.84 THz/RIU and 88.55, respectively. Furthermore, the slow light performance of the structure is investigated, showing a group delay of up to 0.5 picoseconds.

Surface plasmon polariton excitation and propagation in metal tripod systems

Through the activation of a planar gaseous medium consisting of four-level tripod atoms, our approach provides a mechanism to generate the Surface Plasmon Polariton (SPP). We investigate a three-layer structure in which the bottom layer is composed of atoms arranged in a tripod configuration, a metal film is layered in the middle, and a transparent layer of either air or vacuum resides on top. The bottom layer facilitates SPP excitation via amplification in the atom arrangement, caused by three laser beams: control, weak probe, and signal. The electromagnetically induced transparency effect, which can be seen in atoms, compensates for the momentum difference between light and SPP. We can coherently change SPP propagation length by altering control field strength, resonance, and off-resonant detuning. SPP optical gain power, propagation length, penetration depth, and metal thickness effects are also examined. Our method to generate SPPs may find use in lithography, sensors, polarizers, along with photodetectors.

Conductively coupled terahertz metamaterials with dual functions of electromagnetically induced transparent and Fano effects for sensing applications

A terahertz metamaterial structure consisting of two U-shaped split-ring resonators and a horizontal cut-line resonator is designed for realizing the electromagnetically induced transparency (EIT) effect and the Fano resonance effect. The genesis of the EIT and Fano resonance bifunctionality is illustrated by combining the near-field distribution analysis of transparent windows and transmission dips. Interestingly, the bifunctional dual-band transparency effect could transform into a single-functional single-band transparency effect when we change the position of the square metal sheet in the vertical direction of the composited terahertz metamaterial structure. In addition, based on the high-quality factor of Fano resonance response, the proposed bifunctional terahertz metamaterial device has good refractive index sensing sensitivity. These results indicate that our proposed terahertz metamaterial can provide guidance for the design of subsequent multifunctional and integrated metamaterials and optoelectronic devices.

Tunable multifunctional terahertz metamaterial device based on metal-dielectric-vanadium dioxide

The Electromagnetically Induced Transparency (EIT) effect in terahertz (THz) metamaterial devices has garnered extensive attention owing to its distinctive advantages in the slow light devices and quantum communication. However, the application of EIT has been constrained by the limitation to a single transparent window and the fixed intensity of the electromagnetic response at the transmission peak after fabrication. To achieve a dual-frequency EIT effect and enable active tunability, this paper presents a tunable multifunction THz metamaterial device based on vanadium dioxide (VO2). The transition of VO2 from the insulator to the metal allows for the active control of EIT and multi-band absorption switching in the THz range. When VO2 is in its dielectric state, two EIT-like windows could be observed with a maximum value of 86.9 % and 71.7 % of the transmission amplitude, respectively. By adjusting the temperature of the VO2, a modulation depth of up to 99 % can be achieved, enabling active control of the EIT-like effect. In addition, active adjustment of group delay of up to 5.47 ps was demonstrated. When VO2 is in the metallic state, the device serves as a tunable multiband absorber, capable of achieving perfect absorption and modulation amplitude of up to 92 %. The results indicated that the presented devices hold significant value for research in the THz range, particularly for applications related to switching and slow light devices. Therefore, the tunable multifunctional THz metamaterial device is of great significance for THz technology.

Metamaterial-induced-transparency engineering through quasi-bound states in the continuum by using dielectric cross-shaped trimers

This study presents a novel approach to activate a narrowband transparency line within a reflecting broadband window in all-dielectric metasurfaces, in analogy to the electromagnetically-induced transparency effect, by means of a quasi-bound state in the continuum (qBIC). We demonstrate that the resonance overlapping of a bright mode and a qBIC-based nearly-dark mode with distinct Q-factor can be fully governed by a silicon trimer-based unit cell with broken-inversion-symmetry cross shape, thus providing the required response under normal incidence of a linearly-polarized light. Our analysis that is derived from the far-field multipolar decomposition and near-field electromagnetic distributions uncovers the main contributions of different multipoles on the qBIC resonance, with governing magnetic dipole and electric quadrupole terms supplied by distinct parts of the dielectric “molecule”. The findings extracted from this research open up new avenues for the development of polarization-dependent technologies, with particular interest in its capabilities for sensing and biosensing.

Plasmonic induced transparency and slow light integrated device for graphene-based metamaterial

The terahertz excitation characteristics of a graphene-based band structure are studied. This structure has different planar band structures that can excite two bright modes and then it can achieve an excellent plasmonic induced transparency effect through the two bright modes. By analyzing the boundary conditions of the electromagnetic field, the dispersion relationship of this structure can be smoothly obtained. Furthermore, the internal loss factor in the matching coupled mode theory can be calculated. Meanwhile, the tuning performance of this simple structure is analyzed through the external voltage. The Fermi level regulated by voltage is also analyzed, and its influence on the entire tuning mechanism is studied. A detailed analysis is conducted on the slow light performance of this structure, and the influence of Fermi level on the slow light performance is explored. This investigation is expected to provide potential theoretical foundations for slow light, optical storage, and other fields.

Flavor-independent yield of high- pT hadrons from nuclear collisions

Data on high-pT hadron production in heavy ion collisions at Feynman xF=0 indicate at universality of the observed nuclear suppression. Our analysis of the production mechanisms demonstrates important role of the color transparency effects which make the survival probability of a quark-antiquark dipole independent of the quark flavor, provided that the hadron wave function is formed outside the medium. The latter condition imposes restrictions on the range of pT, which should be sufficiently high to make the nuclear suppression universal. We also found that the in-medium broadening rate q^ (frequently called transport coefficient) significantly depends on the quark flavor, diminishing for heavy quarks. Published by the American Physical Society 2024

Unveiling the Interlayer Interaction in a 1H/1T TaS2 van der Waals Heterostructure.

This study delves into the intriguing properties of the 1H/1T-TaS2 van der Waals heterostructure, focusing on the transparency of the 1H layer to the charge density wave of the underlying 1T layer. Despite the sizable interlayer separation and metallic nature of the 1H layer, positive bias voltages result in a pronounced superposition of the 1T charge density wave structure on the 1H layer. The conventional explanation relying on tunneling effects proves insufficient. Through a comprehensive investigation combining low-temperature scanning tunneling microscopy, scanning tunneling spectroscopy, non-contact atomic force microscopy, and first-principles calculations, we propose an alternative interpretation. The transparency effect arises from a weak yet substantial electronic coupling between the 1H and 1T layers, challenging prior understanding of the system. Our results highlight the critical role played by interlayer electronic interactions in van der Waals heterostructures to determine the final ground states of the systems.

Dual-band tunable electromagnetically induced transparency in vanadium dioxide-based miniaturized terahertz metasurfaces

A dual-band electromagnetically induced transparency (EIT) effect with high transmission amplitudes and polarization-insensitive characteristic is realized in vanadium dioxide (VO2)-based miniaturized terahertz metasurfaces. The unit cell comprises a metallic spiral (MS) structure, a small square metal frame (SMF2) structure, and a large square metal frame (SMF1) structure. Two transparent windows with the transmission amplitudes of 0.84 and 0.82 are obtained. The surface current distributions reveal that the dual-band EIT effect is created by the bright-bright-quasi-dark coupling mode. The two transparent windows achieve modulation depths of 45.2% and 42.7%, with maximum group delays of 3.24 ps and 3.17 ps, respectively. The proposed EIT metasurfaces exhibit an electric size of only 0.25λ0, which is considerably smaller than that of other dual-band EIT metasurfaces. The present study offers a novel approach to investigating multi-band EIT metasurfaces, with considerable promise for the development of multi-band communication devices.

Tunable plasmon-induced transparency in anisotropic graphene-black phosphorus photonic device for high-performance sensors and switchers

A novel photonic device composed of graphene and black phosphorus (G-BP) has been proposed, which achieves high-performance plasmon-induced transparency (PIT) effect within the THz range and maintains substantial tunability and anisotropy. The anisotropy of the PIT effect arises from the near-field coupling between two bright modes characterized by distinct effective electron masses of BP, resulting transparency window at 33.35 THz for TE polarization and at 26.92 THz for TM polarization. Through the modulation of Fermi energy in graphene, doping levels of BP and geometric parameters separately, a tunable transparency window is achieved. Notably, the convergence or divergence of the anisotropic transparency windows can be well manipulated with different BP doping levels. Furthermore, the proposed G-BP photonic device exhibits a high sensitivity to changes in the surrounding refractive index and substrates, with a maximum sensitivity of 12.04 THz/RI, rendering it suitable for sensor applications. Overall, the proposed photonic device exhibits notable PIT effects characterized by high anisotropic performance, substantial tunability, great sensitivity, and stability, making it a promising candidate for applications in sensors, polarizers, and switchers.

Nonlinear-Optical Analogies in Nuclear-Like Soliton Reactions: Selection Rules, Nonlinear Tunneling and Sub-Barrier Fusion–Fission

Abstract The main goal of our study is to reveal unexpected but intriguing analogies arising between optical solitons and nuclear physics, which still remain hidden from us. We consider the main cornerstones of the concept of nonlinear optics of nuclear reactions and the well-dressed repulsive-core solitons. On the base of this model, we reveal the most intriguing properties of the nonlinear tunneling of nucleus-like solitons and the soliton self-induced sub-barrier transparency effect. We describe novel interesting and stimulating analogies between the interaction of nucleus-like solitons on the repulsive barrier and nuclear sub-barrier reactions. The main finding of this study concerns the conservation of total number of nucleons (or the baryon number) in nuclear-like soliton reactions. We show that inelastic interactions among well-dressed repulsive-core solitons arise only when a “cloud” of “dressing” spectral side-bands appears in the frequency spectra of the solitons. This property of nucleus-like solitons is directly related to the nuclear density distribution described by the dimensionless small shape-squareness parameter. Thus the Fourier spectra of nucleus-like solitons are similar to the nuclear form factors. We show that the nuclear-like reactions between well-dressed solitons are realized by “exchange” between “particle-like” side bands in their spectra.

All-optical multichannel switch and slow light based on dynamically tunable plasmon-induced transparency

The triple plasmon-induced transparency (PIT) effect based on a metal–insulator–metal waveguide structure comprising two groups of big and small disk resonators (BSDRs) is investigated theoretically and numerically. As a tool employed to explain the PIT, N-order coupled mode theory (CMT), is established, and the calculated results of the triple-PIT effect exhibit excellent consistency with finite-difference time-domain simulations. The influence of the separation between the small disk resonators on the triple-PIT response is discussed in detail through the dynamical equation. Further research shows that the central wavelengths of the triple-PIT transmission window can be adjusted with extremely low pump intensity and ultrafast optical response when monolayer graphene covers the surface of the BSDRs. Meaningfully, light traveling at resonant wavelengths can be effectively slowed down, with the highest group index reaching 368. Based on the PIT effect, a low-power and ultrafast switch is realized with a modulation amplitude of more than 93% at the corresponding wavelengths of the eight depressions. Thus, not only do the insights put forward new ideas, to the best of our knowledge, for highly tunable optoelectronic devices, but the results from the N-order CMT also offer new theory progress and references in the plasmonic waveguide structures.

Multi-channel switch and sensing applications based on multilayered annular graphene metamaterials at terahertz frequency

In this study, a novel silica-graphene–silica periodic graphene structure consisting of six graphene semi-rings is proposed. The structure is based on a three-layer graphene metamaterial with a semicircular ring that achieves a tunable double plasmon-induced transparency (PIT) effect. In the proposed structure, the double-PIT window can be switched simultaneously at multiple frequencies through the dynamic tunability of graphene. Besides, the sensitivities of the refractive index for the PIT windows are investigated with the maximum values of 1.42 THz RIU−1 and 1.09 THz RIU−1, respectively, indicating the structure’s performance as a terahertz sensor. Overall, it shows the potential of PIT effect in graphene metamaterials in controlling electromagnetic field responses. It has made positive contributions to the development of terahertz technology and related fields.

Tunable optical devices with multiple plasmon-induced transparency based on graphene-black phosphorus hybrid metasurface

In this research, we propose a simple and novel graphene-black phosphorus composite structure. Through the coupling mechanism of bright–bright mode, four layers of graphene and one layer of black phosphorus produce a quadruple plasmon-induced transparency (PIT) effect. The response of the proposed structure to the angle of polarized light is investigated, and it is found that the sensitivities of graphene and black phosphorus to the polarization angle of light are different. In addition, the dynamic regulation of PIT by the Fermi level of graphene and the carrier concentration of black phosphorus are discussed. The modulation depths of the fivefold optical switching are 96%, 99%, 87%, 93%, and 80%, respectively. The quadruple PIT can also be converted into triple PIT, in which single, dual, or triple optical switching are realized, respectively. Finally, with the change in the refractive index of the environment medium, the sensitivity response of the proposed structure is as high as 4.790 THz⋅RIU−1. We believe that this research will contribute to the development of optical switches, modulators, and sensors.