Perfect Reflection Research Articles

Broadband low-loss polarization-insensitive graphene-integrated photonic crystal fiber modulators in the near-infrared range

The amplitude modulator with the function of converting electric signal to optical amplitude modulation is a key component in high-speed optical communication links. In this paper, we demonstrate a variety of two-dimensional graphene-integrated photonic crystal fiber modulators for efficient near-infrared amplitude modulation with ultra-low insertion loss. Taking the advantages of the perfect total internal reflection of the porous photonic crystal fiber and flexible tunability of the graphene conductivity, the modulation depth of 0.075 dB μm−1 with a low optical loss of 2.13 × 10−4 dB μm−1, a long propagation length of ∼20 mm and polarization-insensitive characteristics in a wide wavelength of 1.3 to 1.8 μm can be achieved. This high-performance modulator may have great potential applications in various high-speed telecommunication, interconnection, and graphene-based integrated photonic systems.

How might Apple, Freire, and hooks redesign the modern school as a site for social transformation?

In Western society, schools have largely been designed to reproduce capitalist, patriarchal, white supremacist, colonial systems and values. Numerous structural elements—from redlining and modern segregation to scripted curricula and high-stakes testing—work to ensure that schools solidify existing social inequalities, produce good worker bees, and keep hegemonic powers in place. Shaped within these forces of reproduction, our schools are fraught with grave problems: racism and discrimination in every form, physical and emotional bullying, hunger and food insecurity, technology addiction, sexual harassment, teen suicide, conflicts and gang violence, drug use, mindless consumption, and ecological destruction. The modern school is a perfect microcosm and reflection of an unhealthy society. How might we redesign schools such that they become sites of social transformation, rather than reproduction? How might we cultivate kind, ethical, empowered global citizens within our classrooms? In this paper, I will explore how Michael Apple, Paulo Freire, and bell hooks might address these questions. I will explore each scholar’s theories in an attempt to imagine what a school based in their pedagogical philosophy might look like—one that nurtures kind, ethical, and empowered global citizens.

Printing of 3D photonic crystals in titania with complete bandgap across the visible spectrum.

A photonic bandgap is a range of wavelengths wherein light is forbidden from entering a photonic crystal, similar to the electronic bandgap in semiconductors. Fabricating photonic crystals with a complete photonic bandgap in the visible spectrum presents at least two important challenges: achieving a material refractive index > ~2 and a three-dimensional patterning resolution better than ~280 nm (lattice constant of 400 nm). Here we show an approach to overcome such limitations using additive manufacturing, thus realizing high-quality, high-refractive index photonic crystals with size-tunable bandgaps across the visible spectrum. We develop a titanium ion-doped resin (Ti-Nano) for high-resolution printing by two-photon polymerization lithography. After printing, the structures are heat-treated in air to induce lattice shrinkage and produce titania nanostructures. We attain three-dimensional photonic crystals with patterning resolution as high as 180 nm and refractive index of 2.4-2.6. Optical characterization reveals ~100% reflectance within the photonic crystal bandgap in the visible range. Finally, we show capabilities in defining local defects and demonstrate proof-of-principle applications in spectrally selective perfect reflectors and chiral light discriminators.

Natural low-illumination image enhancement based on dual-channel prior information

This paper proposes an adaptive image enhancement method that aims to effectively restore the brightness, detail, and natural color of various low-illumination images. To be specific, the method first constructs the initial dual-channel illumination map of the image. Next, the optimal illumination correction coefficient is calculated by the prior information entropy of the initial illumination map, which helps to correct potentially erroneous illumination estimates. To restore the illumination, gamma correction is used with the optimal illumination correction coefficient. Finally, an improved perfect reflection constraint model is used to restore the color of the image. Both visual analysis and quantitative comparison with state-of-the-art methods demonstrate the effectiveness of the method in terms of brightness adjustment, detail recovery, and color restoration.

Reprogrammable metasurface design for NIR beam steering and active filtering

Reprogrammable metasurfaces enable active modulation of light at subwavelength scales. Operating in the microwave, terahertz, and mid-infrared ranges, these metasurfaces find applications in communications, sensing, and imaging. Electrically tunable metasurfaces operating in the near-infrared (NIR) range are crucial for light detection and ranging (LiDAR) applications. Achieving a NIR reprogrammable metasurface requires individual gating of nano-antennas, emphasizing effective heat management to preserve device performance. To this end, here we propose an electrically tunable Au–vanadium dioxide (VO2) metasurface design on top of a one-dimensional Si–Al2O3 photonic crystal (PC), positioned on a SiC substrate. Each individual Au–VO2 nano-antenna is switched from an Off to ON state via Joule heating, enabling the programming of the metasurface using 1-bit (binary) control. While operating as a nearly perfect reflector at λ0=1.55μm , the materials, thickness, and number of the layers in the PC are carefully chosen to ensure it acts as a thermal metamaterial. Moreover, with high optical efficiency (R ∼ 40% at λ0 ), appropriate thermal performance, and feasibility, the metasurface also enables broadband programmable beam steering in the 1.4−1.7μm range for a wide steering angle range. This metasurface design also offers active control over NIR light transmittance, reflectance and absorptance in the wavelength range of 0.75−3μm . These characteristics render the device practical for LiDAR and active filtering.

Numerical study of nanochannel on a silicon-silver dimer gap for significantly enhanced fluorescence

The metal-dielectric dimer is an ideal structure for enhancing single-molecule fluorescence. When a single-molecule interacts with the metal-dielectric dimer, the metal-dielectric plasmonic system creates strong resonance, which amplifies the electric field by several orders of magnitude. One-dimensional photonic crystals (1D PCs) provide a photonic bandgap (PBG) and nearly perfect reflection for specific wavelengths. These phenomena contribute significantly to fluorescence enhancement. Herein, we propose the structure of 1D PCs with a silicon-silver dimer to achieve remarkable fluorescence enhancement under numerical study. Specifically, our design involves a 20 nm gapped silicon-silver dimer with a 50 nm nanochannel positioned above it. Through the optimization of structural parameters, our results demonstrate that quantum dots with a high intrinsic quantum yield, such as 100 %, are capable of achieving a fluorescence directional emission enhancement of up to three orders of magnitude compared to the bare structure, with an average enhancement factor reaching 407-fold. These findings stand for the unique sensitivity of the device, making it a promising choice for applications in biological nanoparticle detection, environmental monitoring, and other fields in the future.

Frequency-doubling perfect negative reflection in phase gradient metasurfaces

Phase gradient metasurfaces (PGMs) have demonstrated powerful capacities for manipulating light waves freely. However, PGMs have limitations of bulky size and narrow bandwidth that hinder further applications. In this work, we present the design and analysis of a reflection-type PGM by utilizing the phase choice freedom in the supercell. It is found that in this well-designed PGM, perfect negative reflection including perfect retro-reflection can be observed not only at the initially designed frequency f1 = f0, but also at its double frequency, i.e., f2 = 2f0, which is named as the frequency-doubling perfect negative reflection. As a proof of concept, we design and fabricate a reflection-type PGM with 4π phase coverage in a supercell, with experimental results in perfect agreement with the theoretical ones. Our work offers an approach to design planar optical devices at multiple operating frequencies, holding potential applications for frequency division multiplexing communication, remote sensor technology, laser tracking, and more.

Near-infrared metamaterials for tunable wide-band perfect reflection

Achieving perfect reflection with minimal loss and high efficiency is possible through the utilization of all-dielectric metamaterials, capitalizing on Mie resonance in materials with high permittivity. In this study, we introduce a novel approach to create a tunable perfect reflector operating within the near-infrared spectrum. This reflector is constructed using an all-dielectric metamaterial consisting of a SiO2 substrate and a periodic array of Si cuboids. Through precise adjustments in size and period, we demonstrate the attainment of near-perfect reflection across the near-infrared band. Notably, the reflector exhibits a bandwidth of 350.5 nm and maintains an average reflection exceeding 99 % over the spectral range from 1444.5 nm to 1795.0 nm. By customizing the electric and magnetic resonances throughout the near-infrared spectrum, our design offers adaptability to fulfill specific reflection bandwidth requirements. The tunable perfect reflector shows great potential for applications in various fields, including filtering, sensing, and optical communication, offering enhanced performance and versatility.

Amplified Nonreciprocal Reflection in a Uniform Atomic Medium with the Help of Spontaneous Emissions

It is important to elaborate on versatile strategies for achieving the perfect nonreciprocal reflection amplification, which is the key technology of high-quality nonreciprocal photonic devices. In this work, we ingeniously design a coherent four-level N-type atomic system to harness the nonreciprocal light amplification, in which the uniform distribution of atoms is driven by two strong coupling fields and a weak probe field. In our regime, the strength of the two control fields is designed with linear variation along the x direction to destroy the spatial symmetry of the probe susceptibility, leading to the nonreciprocity of the reflection. In particular, the closed-loop transitions to amplify the probe field are due to the combined effect of the control fields and spontaneous emissions. The numerical simulation indicates that the perfect nonreciprocal reflection amplification can be realized and modulated by the appropriate settings of the control fields and the detuning, Δc. Our results will open a new route toward harnessing nonreciprocity, which can provide more convenience and possibilities in experimental realization.

Amber rainbow ribbon effect in broadband optical metamaterials

Using the trapped rainbow effect to slow down or even stop light has been widely studied. However, high loss and energy leakage severely limited the development of rainbow devices. Here, we observed the negative Goos-Hänchen effect in film samples across the entire visible spectrum. We also discovered an amber rainbow ribbon and an optical black hole due to perfect back reflection in optical waveguides, where little light leaks out. Not only does the amber rainbow ribbon effect show an automatic frequency selection response, as predicted by single frequency theoretical models and confirmed by experiments, it also shows spatial periodic regulation, resulting from broadband omnidirectional visible metamaterials prepared by disordered assembly systems. This broadband light trapping system could play a crucial role in the fields of optical storage and information processing when being used to construct ultra-compact modulators and other tunable devices.

Coherent interface between optical and microwave photons on an integrated superconducting atom chip

Sub-wavelength arrays of atoms exhibit remarkable optical properties, analogous to those of phased array antennas, such as collimated directional emission or nearly perfect reflection of light near the collective resonance frequency. We propose to use a single-sheet sub-wavelength array of atoms as a switchable mirror to achieve a coherent interface between propagating optical photons and microwave photons in a superconducting coplanar waveguide resonator. In the proposed setup, the atomic array is located near the surface of the integrated superconducting chip containing the microwave cavity and optical waveguide. A driving laser couples the excited atomic state to Rydberg states with strong microwave transition. Then the presence or absence of a microwave photon in the superconducting cavity makes the atomic array transparent or reflective to the incoming optical pulses of proper frequency and finite bandwidth.

SOI Based metasurface for broadband perfect reflection in visible spectrum

We propose modeling and design of a low-loss all-dielectric metasurface (DM), comprised of Silicon on Insulator (SiO2) substrate to demonstrate a perfect reflector in the visible spectrum. The proposed metasurface unit cell consists of V and W shapes arranged in a mirror image configuration, with nanometre-sized gaps (g) between them. A narrow peak with a nearly 100% reflectance and a broad perfect reflectance spectrum is observed within the visible region (400–700 nm) of the electromagnetic spectrum. The effective electromagnetic parameters were also analyzed for electric and magnetic dipole resonance. The electric and magnetic field distributions at the resonant wavelength were also analyzed for the proposed structure. By altering the gap region ‘g’, the thickness of the dielectric Silica layer (ts ), and the Si resonator (t m), the proposed structure exhibits tunable characteristics. We have successfully illustrated the consistent position of the scattering parameter’s response, regardless of the structure’s rotation, concluding the homogeneity of the designed structure across the entire visible spectrum. The all-DM exhibits a unique combination of features, including a distinct and wide reflectance spectrum as well as a tuned and enhanced electric field which makes it an ideal platform for the applications in filters, color printing, low-loss slow-light devices, and nonlinear optics.

High-efficiency light manipulation using a single layer of folded graphene microribbons

Since its one-atom thickness, it remains an open question to enhance light–matter interactions in graphene, which is usually implemented through external resonant structures such as Fabry–Perot cavity. Here, we propose an alternative scheme to enhance light–matter interactions in a single layer of folded graphene microribbons (FGMRs), and remarkably, for normal incidences rather than oblique incidences in most studies. By optimizing structural parameters (e.g., the location of folding axis and folding angle), three light manipulations such as perfect absorption, perfect reflection, and perfect transmission can be achieved independently. More interestingly, any one of the three functionalities can be actively switched to the other via changing material parameters (Fermi level and carrier mobility ), which is actually the most attractive feature of graphene plasmonics. Finally, we show FGMRs can also support triple functionalities, i.e., via changing material parameters, one of the three functionalities can be switched to the second one and then the third one. Our results will be of great interest to fundamental physics and pave the way for graphene plasmonic device applications.

Possible improvements in effective fill factor using X-ray fluorescent interpixel reflectors.

The spatial resolution of energy-integrating diagnostic CT scanners is limited by interpixel reflectors on the detector, which optically isolate pixels but create dead space. Because the width of the reflector cannot easily be decreased, fill factor diminishes as resolution increases. We propose loading (or mixing) a high-Z element into the reflectors, causing the reflectors to be X-ray fluorescent. Re-emitted characteristic X-rays could be detected in adjacent pixels, increasing the effective fill factor and compensating for fill factor loss with higher-resolution detectors. The purpose of this work is to understand the physical principles of this approach and to analyze its effectiveness using Monte Carlo simulations. Detector pixels were modeled using the GEANT4 Monte Carlo package. The width of the reflector was kept constant at 0.1mm throughout, and we considered pixel pitches between 0.5 and 1mm. The pixelated scintillator material was gadolinium oxysulfide, 3mm thick. The baseline reflector material was chosen to be acrylic, and varying concentrations of a high-Z element were loaded into the material. We assumed that the optical characteristics of pixels were ideal (no absorption within pixels, perfect reflection at boundaries). The detector was irradiated uniformly with 10,000 X-ray photons to estimate its spectral response. The figure of merit was the variance of the detector signal at zero frequency normalized to that of an ideal single-bin photon-counting detector with 100% fill factor. Sensitivity analyses were conducted to understand the effect of varying the high-Z element concentration and the spectrum. Initial simulations suggested that a k-edge near 50keV would be ideal. Gd was therefore selected as the high-Z material. The relative variances for a conventional energy integrating detector without Gd at 1mm pixel pitch (81% fill factor) and 0.5mm pixel pitch (64% fill factor) were 1.38 and 1.74, compared to 1.00 for an ideal photon counting detector, implying a 26% variance penalty for 0.5mm pitch. When 1g/cm3 Gd was loaded into the interpixel reflector, the relative variance improved to 1.27 and 1.43, respectively, implying that the variance penalty for including Gd together with 0.5mm pitch is only 4%. Performance was nearly maximized at 1.0g/cm3 of Gd, but a concentration of 0.5g/cm3 of Gd showed most of the benefit. Improvements depend weakly on kV, with lower kV associated with higher improvements. An external anti-scatter grid was not modeled in our simulations and would reduce the expected benefit, depending greatly on the pitch and dimensionality of the anti-scatter grid. The losses in fill factor associated with smaller pixel pitch can be reduced if Gd or a similar element could be loaded into the interpixel reflector. These improvements in noise efficiency are yet to be verified experimentally.

Internal mechanism of perfect-reflector-backed dielectric gratings to achieve 100% diffraction efficiency.

The work started 20 years ago [Appl. Opt.42, 6255 (2003)APOPAI0003-693510.1364/AO.42.006255] investigating the physical mechanism of multilayer dielectric reflection gratings to achieve 100% diffraction efficiency is completed to offer much deeper insight than before. How different scattering matrix elements of the top periodic surface corrugation contribute to the -1st-order efficiency of such a compound grating is unveiled analytically using a minimum set of real parameters. The two diffraction amplitudes transmitted through the top corrugation play a dominant role in enabling 100% diffraction efficiency. Simple necessary and sufficient conditions for 100% efficiency are derived. Moreover, the role of the reflection phase of the perfect reflector, including the contribution of the optical path between the top corrugation and the reflector, is emphasized.

Relations between Keynes's theory and F. D. Roosevelt's economic policy in the environment of the Great Economic Depression of 1929 - 1933

Purpose of the study: The aim of the article is to show possible relations between economic theory and economic policy using the example of the interactions between the Great Economic Crisis, Keynes' theory, and Roosevelt's economic policy.
 Methodology: The methods used include literature studies and critical analysis of the literature, which are important for the development of a given scientific discipline. The subject of research determines the need to use the historical method. In addition, induction and deduction were used, as well as analysis and synthesis.
 Main Findings: Roosevelt's New Deal program is not a perfect reflection of Keynes's theory. In economic policy, such a model approach seems impossible. Both solutions occur parallel to each other. There are points of great similarity, but there are also visible differences. Adopting the thesis about Roosevelt's independence points to the weakness of orthodox economic theory in the face of economic challenges.
 Applications of the study: importance in the teaching of economic sciences. The teaching of economic sciences plays a key role in shaping the direction and level of economic knowledge in society. Currently, in addition to economic orthodoxy, a heterodox approach plays an important role in this respect. Therefore, it constitutes the basis for independent analysis in this area. The way of presenting issues within the so-called theoretical subjects, such as the history of economic thought,. For a critical analysis of economic phenomena, it seems important to enrich economic theory with pragmatic aspects. The article aims to interest economics students in the relationship between economic theory and economic practice.
 Novelty/Originality of the study: In the context of economic, financial and pandemic crises, considerations regarding the role and importance of economic theory and the scientific discipline itself are important. This is an attempt to answer the question to what extent the achievements of scientists in the field of economics allow us to effectively "get out of the crisis" and to what extent these are ad hoc actions. This is particularly important in the context of changing economic methodology and the relationship between heterodoxy and orthodoxy and the economy in times of uncertainty.

Chiral tunneling through double barrier structure in twisted graphene bilayer

The paper discusses the chiral tunneling of charge carriers through double barrier structure in twisted graphene bilayer. The theoretical analysis investigates the transmission probability for various system parameters under both symmetric and asymmetric barrier conditions. The results reveal that the transmission probability of quasiparticles in the K cone is mirror symmetric to that of Kθ cone about φ=0. Furthermore, the study shows that the transmission changes gradually from perfect transmission to perfect reflection in the normal direction by increasing the incident energy and the barrier height, which is different from the case of monolayer and AB-stacked bilayer graphene. It is also found that the double barrier structure remains, only in certain cases, perfectly transparent for normal or near-normal incidence. The chiral nature of the quasiparticles in graphene causes the tunneling to be highly dependent on the direction and also on the double barrier structure. Interestingly, this characteristic provides additional parameter that allows us to tune the electronic properties of the twisted graphene bilayer. Additionally, we found that the transmission exhibits some sharp resonance peaks, the number and amplitude of which depend on the system parameters. Our results provide a better understanding of chiral tunneling in twisted graphene bilayers through double barrier structures, which may thus offer efficient tools to control the transport properties in future graphene-based nanodevices like transistors and photodetectors.

Perfect non-reciprocal reflection amplification in closed loop coherent gain atomic system

High-performance non-reciprocal photonic devices can improve the efficiency of optical quantum manipulation, information processing, and quantum simulation effectively. The enhanced optical signal can simultaneously amplify the weak signal output by the quantum system and isolate the sensitive quantum system from the back-scattered external noise, which is the core technology of high-performance photonic devices. In our previous work (<ext-link ext-link-type="uri" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="https://doi.org/10.1364/OE.499738">2023 <i>Opt. Express</i> <b>31</b> 38228</ext-link>), we have achieved dynamic control of unidirectional reflection amplification based on four-wave mixing gain and the use of coupling field intensity varying linearly with position. In this work, we design a simple three-level closed loop coherent gain atomic system, setting the intensity of coupling field to be varying with position step shape to break the spatial symmetry of probe susceptibility, and achieving perfect non-reciprocal reflection light amplification. In contrast, the stepped variation of coupling field intensity is easier to adjust in experiment, greatly reducing the difficulty in the experiment. Specifically, the system introduces phase modulation. By changing the phase, the frequency region of probe gain and absorption can be switched, which makes the modulation of reflection amplification more flexible.

All-Angle Scanning Perfect Anomalous Reflection by Using Passive Aperiodic Gratings

All-Angle Scanning Perfect Anomalous Reflection by Using Passive Aperiodic Gratings

ИСПОЛЬЗОВАНИЕ ИНФОРМАЦИОННЫХ РЕСУРСОВ СИСТЕМЫ ВНУТРЕННЕГО КОНТРОЛЯ ПРИ НАЛОГОВОМ МОНИТОРИНГЕ КОМПАНИИ

The main instrument for regulating the company’s activities is financial control. In the current market realities, companies are increasingly showing interest in internal control as the main means of regulation. Proper implementation of the internal monitoring system is the key to the effectiveness of companies. Its analysis is aimed at acquiring a set of tasks that help expand the company’s control features and increase the effectiveness of its further work. The key purpose of using the internal control system in this case is to ensure the most perfect and reliable reflection of information about activities in the financial statements. In this paper, the basic concepts of the internal control and monitoring system of this system are studied. However, the emphasis is on a more detailed coverage of the concept of tax monitoring and consideration of the aspect of methodological recommendations for collecting evidence in tax monitoring.