arXiv subjects

Huanyang Chen

Publications and source records attributed to Huanyang Chen.

At least 55 records · Page 3Linked to original sources

arXiv2017

Coherent perfect absorber and laser in purely imaginary conjugate metamaterials

Conjugate metamaterials, in which the permittivity and the permeability are complex conjugates of each other, possess the elements of loss and gain simultaneously. By employing a conjugate metamaterial with a purely imaginary form, we propose a mechanism for realizing both coherent perfect absorber (CPA) and laser modes, which have been widely investigated in parity-time symmetric systems. Moreover, the general conditions for obtaining CPA and laser modes, including obtaining them simultaneously, are revealed by analyzing the wave scattering properties of a slab made of purely imaginary conjugate metamaterials. Specifically, in a purely imaginary conjugate metamaterial slab with a sub-unity effective refractive index, perfect absorption can be realized for the incident wave from air.

physics.optics↗

arXiv2017

Self-focusing and the Talbot effect in conformal transformation optics

Transformation optics (TO) has been used to propose various novel optical devices. With the help of metamaterials, several intriguing designs, such as invisibility cloaks, have been implemented. However, as the basic units should be much smaller than the working wavelengths to achieve the effective material parameters, and the sizes of devices should be much larger than the wavelengths of illumination to work within the light-ray approximation, it is a big challenge to implement an experimental system that works simultaneously for both geometric optics and wave optics. In this letter, by using a gradient-index micro-structured optical waveguide, we realize a device of conformal transformation optics (CTO) and demonstrate its self-focusing property for geometry optics and Talbot effect for wave optics. In addition, the Talbot effect in such a system has a potential application to transfer digital information without diffraction. Our findings demonstrate the photon controlling ability of CTO in a feasible experiment system.

physics.optics↗

arXiv2016

Generalized Surface Polaritons and their quantum spin Hall effect

Surface polaritons, e.g., surface plasmon polaritons, are invaluable tools in nanophotonics. However, considerable plasmon loss narrows the application regime of plasmonic devices. Here we reveal some general conditions for lossless surface polaritons to emerge at the interface of a gain and a loss media. The gain medium does not only compensate the energy loss, but also modifies surface wave oscillation mechanisms. A new type of surface polaritons induced by the sign switch of the imaginary part of the permittivity across the interface is discovered. The surface polaritons exhibit spin Hall effect due to spin-momentum locking and unique Berry phase. The spin Hall coefficient changes the sign across the parity-time symmetric limit and becomes quantized for perfect metal-dielectric interface and for dielectric-dielectric interface with very large permittivity contrast, carrying opposite topological numbers. Our study opens a new direction for manipulating light with surface polaritons in non-Hermitian optical systems.

physics.optics↗

arXiv2015

Conjugate metamaterials and the perfect lens

In this letter, we show how transformation optics makes it possible to design what we call conjugate metamaterials. We show that these materials can also serve as substrates for making a subwavelength-resolution lens. The so-called "perfect lens", which is a lens that could focus all components of light (including propagating and evanescent waves), can be regarded as a limiting case, in which the respective conjugate metamaterials approach the characteristics of left-handed metamaterials, which have a negative refractive index.

physics.optics↗

arXiv2015

Infinite Maxwell fisheye as a complement for an imaging device

\noindent This manuscript proposes a new imaging medium via isotropic refractive index of heterogeneous medium. We exploit conformal-map to transfers the full Maxwell fisheye into a mapped profile within a unit circle. The imaging resolution of this new profile can be maintained as good as the mirrored Maxwell fisheye profile or its conformally-mapped counterpart in previous literature.

physics.optics↗

arXiv2014

Wavefront Modulation and Subwavelength Diffractive Acoustics with an Acoustic Metasurface

Metasurfaces are a family of novel wavefront shaping devices with planar profile and subwavelength thickness. Acoustic metasurfaces with ultralow profile yet extraordinary wave manipulating properties would be highly desirable for improving the performance of many acoustic wave-based applications. However, designing acoustic metasurfaces with similar functionality as their electromagnetic counterparts remains challenging with traditional metamaterial design approaches. Here we present a design and realization of an acoustic metasurface based on tapered labyrinthine metamaterials. The demonstrated metasurface can not only can steer an acoustic beam as expected from the generalized Snell s law, but also exhibits various unique properties including surface wave conversion, extraordinary beam-steering and apparent negative refraction through higher-order diffraction. Such designer acoustic metasurfaces provide a new design methodology for acoustic signal modulation devices and may be useful for applications such as beam-steering, surface wave manipulation, high efficiency sound absorption, acoustic imaging and ultrasound lens design.

cond-mat.mtrl-sci↗

arXiv2013

Transformation optics with Fabry-Pérot resonances

Transformation optics is a powerful tool to design various novel devices, such as invisibility cloak. Fantastic effects from this technique are usually accompanied with singular mappings, resulting in challenging implementations and narrow bands of working frequencies. Here in this article, we find that Fabry-Pérot resonances can be used to design various transformation optical devices that are not only easy to realize but also can work well for a set of resonant frequencies (multiple frequencies). As an example, we fabricate a prototype for a cylindrical concentrator for microwaves.

physics.optics↗

arXiv2013

Revisit the carpet cloak from optical conformal mapping

The original carpet cloak [Phys. Rev. Lett. 101, 203901 (2008)] was designed by a numerical method, the quasi-conformal mapping. Therefore its refractive index profile was obtained numerically. In this letter, we propose a new carpet cloak based on the optical conformal mapping, with an analytical form of a refractive index profile, thereby facilitating future experimental designs.

physics.optics↗

arXiv2012

Cloaking and imaging at the same time

In this letter, we propose a conceptual device to perform subwavelength imaging with positive refraction. The key to this proposal is that a drain is no longer a must for some cases. What's more, this device is an isotropic omnidirectional cloak with a perfect electric conductor hiding region and shows versatile illusion optical effects. Numerical simulations are performed to verify the functionalities.

physics.optics↗

arXiv2012

Realizing bending waveguides with anisotropic epsilon-near-zero metamaterials

We study metamaterials with an anisotropic effective permittivity tensor in which one component is near zero. We find that such an anisotropic metamaterial can be used to control wave propagation and construct almost perfect bending waveguides with a high transmission rate (>95%). This interesting effect originates in the power flow redistribution by the surface waves on the input and output interfaces, which smoothly matches with the propagating modes inside the metamaterial waveguide. We also find that waves in such anisotropic epsilon-near-zero materials can be reflected by small-sized perfect magnetic conductor defects. Numerical calculations have been performed to confirm the above effects.

physics.optics↗

arXiv2012

Generalized laws of reflection and refraction from transformation optics

Based on transformation optics, we introduce another set of generalized laws of reflection and refraction (differs from that of [Science 334, 333 (2011)]), through which a transformation media slab is derived as a meta-surface, producing anomalous reflection and refraction for all polarizations of incident light.

physics.optics↗

arXiv2012

Collimating lenses from non-Euclidean transformation optics

Based on the non-Euclidean transformation optics, we design a thin metamaterial lens that can achieve wide-beam radiation by embedding a simple source (a point source in three-dimensional case or a line current source in two-dimensional case). The scheme is performed on a layer-by-layer geometry to convert curved surfaces in virtual space to flat sheets, which pile up and form the entire lens in physical space. Compared to previous designs, the lens has no extreme material parameters. Simulation results confirm its functionality.

physics.optics↗

arXiv2011

On conformal lenses

Plane mirror can make one object into two for observers on the object's side. Yet, there seems no way to achieve the same effect for observers from all directions. In this letter, we will design a new class of gradient index lenses from multivalued optical conformal mapping. We shall call them the conformal lenses. Such lenses can transform one source into two (or even many) omnidirectionally. Like the overlapped illusion optics does, they can even transform multiple sources into one. Rather than using negative index materials, implementation here only needs isotropic positive index materials like other gradient index lenses. One obvious drawback however, is that they have singular permittivity values which restrict them to functioning at one single frequency. This however, needs not be the case when applying transmutation methods, which enable the lenses to work in a broadband frequency range.

physics.optics↗

arXiv2011

Conformal cloak for waves

Conformal invisibility devices are only supposed to work within the validity range of geometrical optics. Here we show by numerical simulations and analytical arguments that for certain quantized frequencies they are nearly perfect even in a regime that clearly violates geometrical optics. The quantization condition follows from the analogy between the Helmholtz equation and the stationary Schrodinger equation.

physics.optics↗

arXiv2011

Electromagnetically induced Talbot effect

By modulating transmission function of a weak probe field via a strong control standing wave, an electromagnetically induced grating can be created in the probe channel. Such a nonmaterial grating may lead to self-imaging of ultra-cold atoms or molecules in the Fresnel near-field regime. This work may offer a nondestructive and lensless way to image ultra-cold atoms or molecules.

physics.optics↗

arXiv2010

Total reflection and transmission by epsilon-near-zero metamaterials with defects

In this work, we investigate wave transmission through an epsilon-near-zero metamaterial waveguide embedded with defects. We show that by adjusting the geometric sizes and material properties of the defects, total reflection and even transmission can be obtained, despite the impedance mismatch of epsilon-near-zero material with free space. Our work can greatly simplify the design of zero-index material waveguide applications by removing the dependence on permeability.

physics.optics↗

arXiv2010

Anti-mirror effect: A perfect lens brings a brighter feature

In this letter, we show that a perfect lens can be employed to make multiple objects appear like only one in the far field, leading to a new concept of illusion optics. Numerical simulations are performed to verify the functionalities for both passive and active objects. The conceptual device can be utilized to enhance the illumination brightness for both incoherent and coherent systems.

physics.optics↗

arXiv2010

An invisibility cloak using silver nanowires

In this paper, we use the parameter retrieval method together with an analytical effective medium approach to design a well-performed invisible cloak, which is based on an empirical revised version of the reduced cloak. The designed cloak can be implemented by silver nanowires with elliptical cross-sections embedded in a polymethyl methacrylate host. This cloak is numerically proved to be robust for both the inner hidden object as well as incoming detecting waves, and is much simpler thus easier to manufacture when compared with the earlier proposed one [Nat. Photon. 1, 224 (2007)].

physics.optics↗