Quantum optical analysis of squeezed state of light through dispersive non-Hermitian optical bilayers

We investigate the propagation of a normally incident squeezed coherent state of light through dispersive non-Hermitian optical bilayers, particularly at a frequency that the bilayers hold parity-time (PT) symmetry. To check the realization of PT-symmetry in quantum optics, we reveal how dispersion and loss/gain-induced noises and thermal effects in such bilayers can affect quantum features of the incident light, such as squeezing and sub-Poissonian statistics. The numerical results show thermally-induced noise at room temperature has an insignificant effect on the propagation properties in these non-Hermitian bilayers. Moreover, tuning the bilayers’ loss/gain strength, we show that the transmitted squeezed coherent states through the structure can retain to some extent their nonclassical characteristics, specifically for the frequencies far from the emission frequency of the gain layer. Furthermore, we demonstrate, only below a critical value of gain, quantum optical effective medium theory can correctly predict the propagation of quantized waves in non-Hermitian and PT-symmetric bilayers.

Effective Medium Theory of Metamaterials and Metasurfaces

Metamaterials, including their two-dimensional counterparts, are composed of subwavelength-scale artificial particles. These materials have novel electromagnetic properties, and can be artificially tailored for various applications. Based on metamaterials and metasurfaces, many abnormal physical phenomena have been realized, such as negative refraction, invisible cloaking, abnormal reflection and focusing, and many new functions and devices have been developed. The effective medium theory lays the foundation for design and application of metamaterials and metasurfaces, connecting metamaterials with real world applications. In this Element, the authors combine these essential ingredients, and aim to make this Element an access point to this field. To this end, they review classical theories for dielectric functions, effective medium theory, and effective parameter extraction of metamaterials, also introducing front edge technologies like metasurfaces with theories, methods, and potential applications. Energy densities are also included.

A Composite Matching Layer with Anti-Reflection Characteristics for Broadband Acoustic Scattering Reduction

A composite matching layer composed of periodically arranged scatters with anti-reflection (AR) characteristics is proposed for broadband scattering reduction. The anti-reflection structure is composed of periodically arranged metal foam scatters, and it is the first attempt to be applied in the field of suppressing acoustic reflection. A complete theoretical model is developed to reveal the mechanism of scattering reduction and acoustic absorption based on effective medium theory and the transfer matrix method. The correctness and effectiveness of the theoretical model are verified by the finite element method (FEM), showing acoustic reflectance of less than 13.5% at broadband frequencies. The variation trends of reflectance are deeply investigated. The superior acoustic scattering reduction performance suggests that the matching layer possesses potential for acoustic imaging equipment and acoustic stealth.

Negative refraction in twisted hyperbolic metasurfaces

Hyperbolic metasurfaces with unique dispersion properties can manipulate light–matter interactions according to the demands. However, due to their inherent physical properties, topological transitions (flat bands) exist only in the orthogonal directions, which greatly limit their application. Here, we unveil rich dispersion engineering and topological transitions in hyperbolic metasurfaces. Based on the effective medium theory, the rotation matrix is introduced into the dispersion relation to explain the distorted energy band diagrams, iso-frequency contours and higher-order multi-dipoles of the novel twisted metasurfaces, thereby forming multi-directional topological transitions and surface plasmon polariton propagation. Furthermore, we develop an integrated model to realize new dual-channel negative refraction and nondiffraction negative refraction. The phenomena observed in the experiments match well with the simulations, which proves that the designed metasurfaces make new types of negative refraction possible and will help to overcome the diffraction limit. The hyperbolic metasurfaces presented here exhibit exceptional capabilities for designing microscopes with a super lens at the molecular level, concealment of military aircraft, invisibility cloaks and other photonic devices with higher transmission efficiency.

Field Decorrelation and Isolation Improvement in an MIMO Antenna Using an All-Dielectric Device Based on Transformation Electromagnetics

This work presents a new technique for enhancing the performance of a multiple-input multiple-output (MIMO) antenna by improving its correlation coefficient ρ. A broadband dielectric structure is designed using the transformation electromagnetics (TE) concept to decorrelate the fields of closely placed radiating elements of an MIMO antenna, thereby decreasing ρ and mutual coupling. The desired properties of the broadband dielectric wave tilting structure (DWTS) are determined by using quasi-conformal transformation electromagnetics (QCTE). Next, the permittivity profile of the DWTS is realized by employing air-hole technology, which is based on the effective medium theory, and the DWTS is fabricated using the additive manufacturing (3D printing) technique. The effectiveness of the proposed technique is verified by designing two-element patch-based MIMO antenna prototypes operating at 3 GHz, 5 GHz, and 7 GHz, respectively. The proposed technique helped to reduce the correlation coefficient ρ in the range of 37% to 99% in the respective operating bandwidth of each MIMO antenna, thereby, in each case, improving the isolation between antenna elements by better than 3 dB, which is an excellent performance.

A scheme for simulating multi-level phase change photonics materials

Chalcogenide phase change materials (PCMs) have been extensively applied in data storage, and they are now being proposed for high resolution displays, holographic displays, reprogrammable photonics, and all-optical neural networks. These wide-ranging applications all exploit the radical property contrast between the PCMs’ different structural phases, extremely fast switching speed, long-term stability, and low energy consumption. Designing PCM photonic devices requires an accurate model to predict the response of the device during phase transitions. Here, we describe an approach that accurately predicts the microstructure and optical response of phase change materials during laser induced heating. The framework couples the Gillespie Cellular Automata approach for modelling phase transitions with effective medium theory and Fresnel equations. The accuracy of the approach is verified by comparing the PCM’s optical response and microstructure evolution with the results of nanosecond laser switching experiments. We anticipate that this approach to simulating the switching response of PCMs will become an important component for designing and simulating programmable photonics devices. The method is particularly important for predicting the multi-level optical response of PCMs, which is important for all-optical neural networks and PCM-programmable perceptrons.

Multi-physics evaluation of carbonate-rich source rocks from high-resolution images

In unconventional reservoirs, the pore space is hosted by a heterogeneous matrix with various minerals and organic components. This heterogeneity complicates petrophysical interpretation during hydrocarbon exploration. A digital rock physics study of thermal and electrical conductivity was conducted using high-resolution focused ion beam scanning electron microscopy images of carbonate-rich source rocks. Finite-volume simulation results are discussed in context of the sample heterogeneity and anisotropy and supported by comparisons to empirical equations and effective medium theory. The results show how the presence of organic matter, pyrite, and pore constrictions impacts application of empirical equations and simplified models to unconventional reservoirs. Graphic abstract