arXiv subjects

Huanyang Chen

Publications and source records attributed to Huanyang Chen.

At least 19 recordsLinked to original sources

arXiv2026

Direction-Selective Wave Freezing and Amplification at a Hyperbolic Time Interface

Hyperbolic media are well known for converting high k-components that are evanescent in conventional dielectrics into propagating bulk waves through their open equifrequency contours. Here, we reveal a complementary temporal effect: after a sudden transition into an effectively nondispersive hyperbolic state, conservation of the full wavevector causes the indefinite dispersion to partition momentum space into real-, zero-, and purely imaginary-frequency regimes. Consequently, p-polarized waves undergo conventional temporal scattering, critical magnetic-field freezing, or exponential growth and decay, depending solely on their conserved wavevector direction, whereas s-polarized waves remain in the real-frequency regime. A second temporal boundary releases the frozen or amplified fields into propagating waves at original frequency. Analytical temporal boundary theory, k-space pulse reconstruction, and finite-difference time-domain simulations corroborate these dynamics. These results establish hyperbolic temporal boundaries as a compact route to direction-selective imaginary frequency dynamics and wave amplification without Floquet periodicity.

physics.optics↗

arXiv2026

Torus-Projected Electromagnetic Wormholes Enabled by Anisotropic Singularity Reconstruction of Metamaterials

Transformation optics uses coordinate mappings to emulate curved geometries and control electromagnetic fields. However, existing approaches primarily focus on geometric deformation while offering limited control over the global topology of the resulting optical space. Here we introduce a torus projection combined with a conformal mapping to construct a wormhole-like virtual optical geometry, providing a controllable route to manipulate virtual space topology within transformation optics. By tuning a single torus parameter, the virtual-space refractive index switches between isotropic and anisotropic forms, driving a transition from a disconnected horn-torus geometry to a connected ring-torus geometry in virtual space. In physical space, this virtual-space topology transition gives rise to switchable black-hole-like trapping, field redistribution, and geometry-controlled wave responses. Our results demonstrate how refractive-index anisotropy governs singularity structure and topology in transformation optics, while also suggesting practical functionalities including beam splitting, absorbing-like switching, and curvature-assisted focusing.

physics.optics↗

arXiv2025

Hyperbolic Continuous Topological Transition in Real Space

Hyperbolic topological transitions refer to the transformation of is isofrequency contours in hyperbolic materials from one topology (e.g., hyperbolic) to another (e.g., elliptical or a different hyperbolic topology). However, current research remains limited to investigating topological transitions in momentum space, thereby hindering the simultaneous real-space observation of distinct hyperbolic states and their associated topological transitions within a single system. In this work, we investigate real-space hyperbolic continuous topological transitions using gradient-index (GRIN) lenses, exemplified by hyperbolic Luneburg lens. By introducing Wick rotations, we demonstrate how spatially modulated refractive indices, mediated by variations in out-of-plane permittivity, drive continuous transitions between hyperbolic Type I and Type II topologies. Furthermore, using a harmonic oscillator model, we uncover the intrinsic relationship between the parameter E of hyperbolic Luneburg lens and its predominant topological behavior, whether hyperbolic Type I or Type II, and extend this concept to a broader framework of Morse lenses. This work provides a theoretical foundation for designing materials with tunable topological properties, advancing applications in photonics, metamaterials, and beyond.

physics.optics↗

arXiv2025

Double Negative Metamaterials in Water Waves

Water waves present both opportunities and hazards, which demand precise control to effectively exploit their energy and mitigate their destructive effects. Leveraging the unique propagation characteristic of negative refraction enables versatile strategies for achieving such control. Here, we propose a Veselago-Pendry double negative metamaterial (DNM) for water waves constructed by nested gears and split tubes. This uniform array structure realizes effective negative water depth and gravity distributions, enabling tunable negative refraction that resolves the unclear structure-propagation relationships and stringent layout requirements of prior negative refraction structures. By employing coherent potential approximation (CPA), negative effective water depth ue and gravity ge are predicted. The predicted DNM parameters align well with band structures, and are validated by simulations of isolation, wave bending and all-angle imaging with surface waves excitation. A simplified experiment demonstrating water wave bending was successfully performed, matching the analytical predictions and simulation results well. Through quantitative mapping between structural parameters and propagation properties that enables tunable bandgaps and controllable negative refraction, DNMs furnish a transformative toolkit for coastal engineering, and are able to calm harbors, boost wave-energy harvesters, and steer river-bend currents to curb erosion.

physics.app-ph↗

arXiv2025

Manifold Optics

Transformation optics establishes an equivalence relationship between gradient media and curved space, unveiling intrinsic geometric properties of gradient media. However, this approach based on curved spaces is concentrated on two-dimensional manifolds, namely curved surfaces. In this Letter, we establish an intrinsic connection between three-dimensional manifolds and three-dimensional gradient media in transformation optics by leveraging the Yamabe problem and Ricci scalar curvature, a measure of spatial curvature in manifolds. The invariance of the Ricci scalar under conformal mappings is proven. Our framework is validated through the analysis of representative conformal optical lenses.

physics.optics↗

arXiv2025

Effects of off-diagonal permittivity terms on polarization singularities in anisotropic grating system

The evolutions of polarization singularities, including bound states in the continuum (BICs) and circularly polarized states (C points), are usually realized by tuning the geometric parameters of photonic crystal slabs. Here, we use the off-diagonal terms of permittivity tensor to manipulate polarization singularities without breaking the structural symmetry in an anisotropic grating system. By controlling the optical axis of anisotropic media, BICs can be shifted to different positions or split into C points, meanwhile, the creation and annihilation of multiple C points are also observed during the evolution process for both TE and TM modes, respectively. Remarkably, two different splitting directions of BICs can be achieved by tuning the off-diagonal terms of permittivity tensor for the two modes. This work illustrates the important role of off-diagonal terms on the far-field polarization singularities and provide an alternative way to precisely manipulate optical singularities

physics.optics↗

arXiv2025

Hyperbolic absolute instruments

As a lens capable of sending images of deep sub-wavelength objects to the far field, the hyperlens has garnered significant attention for its super-resolution and magnification capabilities. However, traditional hyperlenses require extreme permittivity ratios and fail to achieve geometrically perfect imaging, significantly constraining their practical applications. In this paper, we introduce the general versions of hyperbolic absolute instruments from the perspective of dispersion and fundamental optical principles. These instruments enable the formation of closed orbits in geometric optics, allowing hyperlenses to achieve aberration-free, perfect imaging. This development not only provides a flexible and practical tool for enhancing the performance of traditional hyperlens, but also opens new possibilities for new optoelectronics applications based on hyperbolic ray dynamics.

physics.optics↗

arXiv2025

Natural van der Waals canalization lens for non-destructive nanoelectronic circuit imaging and inspection

Optical inspection has long served as a cornerstone non-destructive method in semiconductor wafer manufacturing, particularly for surface and defect analysis. However, conventional techniques such as bright-field and dark-field scattering optics face significant limitations, including insufficient resolution and the inability to penetrate and detect buried structures. Atomic force microscopy (AFM), while offering higher resolution and precise surface characterization, is constrained by slow speed, limited to surface-level imaging, and incapable of resolving subsurface features. Here, we propose an approach that integrates the strengths of dark-field scattering optics and AFM by leveraging a van der Waals (vdW) canalization lens based on natural biaxial α-MoO3 crystals. This method enables ultrahigh-resolution subwavelength imaging with the ability to visualize both surface and buried structures, achieving a spatial resolution of 15 nm and grating pitch detection down to 100 nm. The underlying mechanism relies on the unique anisotropic properties of α-MoO3, where its atomic-scale unit cells and biaxial symmetry facilitate the diffraction-free propagation of both evanescent and propagating waves via a flat-band canalization regime. Unlike metamaterial-based superlenses and hyperlenses, which suffer from high plasmonic losses, fabrication imperfections, and uniaxial constraints, α-MoO3 provides robust and aberration-free imaging in multiple directions. We successfully applied this approach to high-resolution inspection of buried nanoscale electronic circuits, offering unprecedented capabilities essential for next-generation semiconductor manufacturing.

physics.optics↗

arXiv2024

Cosmology analogy for perfect hyperlens

With the emergence of super-resolution lenses such as superlens and hyperlens, coupled with advancements in metamaterials, the diffraction limit of approximately half wavelength is no longer unbreakable. However, superlenses are easily affected by weak intrinsic losses and hyperlenses cannot achieve perfect imaging, significantly constraining their practical utility. To address these challenges, here we propose a perfect hyperlens based on the metric of de Sitter spacetime in cosmology. Importantly, perfect hyperlens is capable of self-focusing in geometrical optics while supporting propagating waves with exceptionally large wavenumbers, which endows it with key advantages such as ultra-high resolution, no aberration and strong robustness. Furthermore, we demonstrate the hyperbolic focusing performance and mimic the de Sitter spacetime in naturally in-plane hyperbolic polaritons of α-MoO3 films numerically, which can be achieved with a gradient thickness profile. Our work provides cosmological insights into the field regulation in hyperbolic materials, greatly innovates the design principles of traditional imaging lenses.

physics.optics↗

arXiv2024

Realizing topologically protected ghost surface polaritons by lattice transformation optics

While conventional surface waves propagate along the surface and decay perpendicularly from the interface, the ghost surface polaritons show oblique propagation direction with respect to the interface. Here, we have discovered topologically protected ghost surface polaritons by applying the lattice transformation optics method to gyromagnetic photonic crystals. By introducing the transformation optics method to periodic systems, we develop the lattice transformation optics method to engineer the band structures and propagation directions of the surface polaritons. We show that a simple shear transformation on the square lattice can tailor the propagation directions with ease. The reversed ghost surface polariton is discovered by setting a negative shear factor. Interestingly, we find the topological invariant Chern number will change sign when the orientation of the Brillouin zone flipped during the transformation. Our findings open up new avenues for studying ghost surface polaritons and provide a general engineering method for periodic systems.

physics.optics↗

arXiv2023

Control water waves by metagratings

Metasurfaces and metagratings offers new platforms for electromagnetic wave control with significant responses. However, metasurfaces based on abrupt phase change and resonant structures suffer from the drawback of high loss and face challenges when applied in water waves. Therefore, the application of metasurfaces in water wave control is not ideal due to the limitations associated with high loss and other challenges. We have discovered that non-resonant metagratings exhibit promising effects in water wave control. Leveraging the similarity between bridges and metagratings, we have successfully developed a water wave metagrating model inspired by the Luoyang Bridge in ancient China. We conducted theoretical calculations and simulations on the metagrating and derived the equivalent anisotropic model of the metagrating. This model provides evidence that the metagrating has the capability to control water waves and achieve unidirectional surface water wave. The accuracy of our theory is strongly supported by the clear observation of the unidirectional propagation phenomenon during simulation and experiments conducted using a reduced version of the metagrating. It is the first time that the unidirectional propagation of water waves has been seen in water wave metagrating experiment. Above all, we realize the water wave metagrating experiment for the first time. By combining complex gratings with real bridges, we explore the physics embedded in the ancient building-Luoyang Bridge, which are of great significance for the water wave metagrating design, as well as the development and preservation of ancient bridges.

physics.ao-ph↗

arXiv2023

Mirrored Transformation Optics

A mirrored transformation optics (MTO) approach is presented to overcome the material mismatch in transformation optics. It makes good use of the reflection behavior and introduce a mirrored medium to offset the phase discontinuities. Using this approach, a high-performance planar focusing lens of transmission-type is designed, which has large concentration ratio than other focusing lens obtained by generalized Snell law. The MTO will not change any functionality of the original lens and promising potential applications in imaging and light energy harvesting.

physics.optics↗

arXiv2022

A dynamically discovered and characterized non-accreting neutron star -- M dwarf binary candidate

Optical time-domain surveys can unveil and characterize exciting but less-explored non-accreting and/or non-beaming neutron stars (NS) in binaries. Here we report the discovery of such a NS candidate using the LAMOST spectroscopic survey. The candidate, designated LAMOST J112306.9+400736 (hereafter J1123), is in a single-lined spectroscopic binary containing an optically visible M star. The star's large radial velocity variation and ellipsoidal variations indicate a relatively massive unseen companion. Utilizing follow-up spectroscopy from the Palomar 200-inch telescope and high-precision photometry from TESS, we measure a companion mass of $1.24_{-0.03}^{+0.03}~M_{\odot}$. Main-sequence stars with this mass are ruled out, leaving a NS or a massive white dwarf (WD). Although a massive WD cannot be ruled out, the lack of UV excess radiation from the companion supports the NS hypothesis. Deep radio observations with FAST yielded no detections of either pulsed or persistent emission. J1123 is not detected in numerous X-ray and gamma-ray surveys. These non-detections suggest that the NS candidate is not presently accreting and pulsing. Our work exemplifies the capability of discovering compact objects in non-accreting close binaries by synergizing the optical time-domain spectroscopy and high-cadence photometry.

astro-ph.SR↗

arXiv2022

Vortex-induced Shear Polaritons

Hyperbolic shear polaritons (HShPs) emerge with widespread attention as a new class of polariton modes with broken symmetry due to shear lattices. In this letter, we find a new mechanism of generating HShPs. When utilizing vortex waves as excitation sources of hyperbolic materials without off-diagonal elements, HShPs will appear. In addition, this asymmetric HShPs can be recovered as symmetric modes away from the source, with a critical transition mode between the left-skewed and right-skewed HShPs, via tuning the magnitude of the off-diagonal imaginary component and controlling the topological charge of vortex source. It is worth mentioning that we explore the influence of parity of topological charges on the field distribution and demonstrate these exotic phenomena from numerical and analytical perspectives. Our results will promote new opportunities for both HShPs and vortex waves, widening the horizon for various hyperbolic materials based on vortex sources and offering a new degree of freedom to control various kinds of polaritons.

physics.optics↗

arXiv2022

Conformal optical black hole for cavity

Whispering gallery mode (WGM) cavity is important for exploring physics of strong light-matter interaction. Yet it suffers from the notorious radiation loss universally due to the light tunneling effect through the curved boundary. In this work, we propose and demonstrate an optical black hole (OBH) cavity based on transformation optics. The radiation loss of all WGMs in OBH cavity is completely inhibited by an infinite wide potential barrier. Besides, the WGM field outside the cavity is revealed to follow $1/r^α$ decay rule based on conformal mapping, which is fundamentally different from the conventional Hankel-function distributions in a homogeneous cavity. Experimentally, a truncated OBH cavity is achieved based on the effective medium theory, and both the Q-factor enhancement and tightly confined WGM field are measured in the microwave spectra which agree well with the theoretical results. The circular OBH cavity is further applied to the arbitrary-shaped cavities including single-core and multi-core structures with high-Q factor via the conformal mapping. The OBH cavity design strategy can be generalized to resonant modes of various wave systems, such as acoustic and elastic waves, and finds applications in energy harvesting and optoelectronics.

physics.class-ph↗

arXiv2022

p-orbital disclination states in non-Euclidean geometries

Disclinations are ubiquitous lattice defects existing in almost all crystalline materials. In two-dimensional nanomaterials, disclinations lead to the warping and deformation of the hosting material, yielding non-Euclidean geometries. However, such geometries have never been investigated experimentally in the context of topological phenomena. Here, by creating the physical realization of disclinations in conical and saddle-shaped acoustic systems, we demonstrate that disclinations can lead to topologically protected bound modes in non-Euclidean surfaces. In the designed honeycomb sonic crystal for p-orbital acoustic waves, non-Euclidean geometry interplay with the p-orbital physics and the band topology, showing intriguing emergent features as confirmed by consistent experiments and simulations. Our study opens a pathway towards topological phenomena in non-Euclidean geometries that may inspire future studies on, e.g., electrons and phonons in nanomaterials with curved surfaces.

cond-mat.mes-hall↗

arXiv2022

Tailoring topological transition of anisotropic polaritons by interface engineering in biaxial crystals

Polaritons in polar biaxial crystals with extreme anisotropy offer a promising route to manipulate nanoscale light-matter interactions. The dynamical modulation of their dispersion is great significance for future integrated nano-optics but remains challenging. Here, we report a momentum-directed strategy, a coupling between the modes with extra momentum supported by the interface and in-plane hyperbolic polaritons, to tailor topological transitions of anisotropic polaritons in biaxial crystals. We experimentally demonstrate such tailored polaritons at the interface of heterostructures between graphene and α-phase molybdenum trioxide (α-MoO3). The interlayer coupling can be electrically modulated by changing the Fermi level in graphene, enabling a dynamic topological transition. More interestingly, we found that the topological transition occurs at a constant Fermi level when tuning the thickness of α-MoO3. The momentum-directed strategy implemented by interface engineering offers new insights for optical topological transitions, which may shed new light for programmable polaritonics, energy transfer and neuromorphic photonics.

physics.optics↗

arXiv2021

Square Maxwell's fish-eye lens for broadband achromatic super-resolution imaging

Broadband super-resolution imaging is important in optical field. To achieve super-resolution imaging, various lenses from superlens to solid immersion lens have been designed and fabricated in recent years. However, the imaging is unsatisfactory due to low work efficiency and narrow band. In this work, we propose a solid immersion square Maxwell's fish-eye lens which realizes broadband (7-16GHz) achromatic super-resolution imaging with full width at half maximum around 0.2 wavelength based on transformation optics at microwave frequencies. In addition, a super-resolution information transmission channel is also designed to realize long-distance multi-source super-resolution information transmission based on the super-resolution lens.

physics.app-ph↗