Generalized refraction using lenslet arrays

用于解决激光导星拉长问题的基于超表面的环透镜阵列设计

Metasurface-based Toroidal Lenslet Array Design for Addressing Laser Guide Star Elongation

针对巨型麦哲伦望远镜激光导星拉长问题，提出基于纳米工程超光学元件的超透镜阵列设计，实现空间变化的变形图像比例压缩，在8mm焦距下提供约100%图像缩减，有效改善波前传感信息采样。

Explaining negative refraction without negative refractive indices

Negative refraction through a triangular prism may be explained without assigning a negative refractive index to the prism by using array theory. For the case of a beam incident upon the wedge, the array theory accurately predicts the beam transmission angle through the prism and provides an estimate of the frequency interval at which negative refraction occurs. Negative refraction effects not only occur in prisms made of traditional metamaterial unit cells, such as magneto-dielectric spheres, but also in solid prisms made of completely filled, homogenous unit cells. In both prisms, the hypote…

An antisymmetric plasmon resonance in coupled gold nanoparticles as a sensitive tool for detection of local index of refraction

A nanofabricated regular array of coupled gold nano-pillars is employed to detect local indices of refraction of different liquids using a shift of an antisymmetric plasmon resonance peak observed in the reflection spectra. The peak spectral position is found to be a unique function of the local refractive index for a wide range of indices. We discuss possible applications of the fabricated nanostructured arrays in bio and chemical sensors.

Negative refraction and spatial echo in optical waveguide arrays

The special symmetry properties of the discrete nonlinear Schrodinger equation allow a complete revival of the initial wavefunction. That is employed in the context of stationary propagation of light in a waveguide array. As an inverting system we propose a short array of almost isolated waveguides which cause a relative pi phase shift in the neighboring waveguides. By means of numerical simulations of the model equations we demonstrate a novel mechanism for the negative refraction of spatial solitons.

非局域双线超材料中的非对称负折射

Asymmetric Negative Refraction in Nonlocal Double-Wire Metamaterials

本研究展示异质双线超材料通过非局域响应实现损耗非对称双曲色散，产生角度选择性的非对称负折射，为定向能量传输和角度选择性波控提供新途径。

Negative Index of Refraction in Optical Metamaterials

An array of pairs of parallel gold nanorods is shown to have a negative refractive index n'=-0.3 at the optical communication wavelength of 1.5 micron. This effect results from the plasmon resonance in the pairs of nanorods for both the electric and magnetic components of light. The refractive index is retrieved from the direct phase and amplitude measurements for transmission and reflection, which are all in excellent agreement with our finite difference time domain simulations. The refraction critically depends on the phase of the transmitted wave, which emphasizes the importance of phase me…

Experimental demonstration of negative index of refraction

We introduce an improved and simplified structure made of periodic arrays of pairs of H-shaped metallic wires that offer a potentially simpler approach in building negative-index materials. Using simulations and microwave experiments, we have investigated the negative-index n properties of these structures. We have measured experimentally both the transmittance and the reflectance properties and found unambiguously that a negative refractive index with Re(n)<0 and Im(n) <Re(n). The same is true for epsilon and mu. Our results show that H-shaped wire pairs can be used very effectively in produc…

Direct wavefront sensing from extended objects: a general sensor

Wavefront sensing from an extended object is a challenging task since the phase to be sensed is disturbed by the phase generated from the structure of the extended object. To address this problem, a general wavefront sensor was proposed. The hardware of the sensor consists of a field lens, a collimating lens, a lenslet array, and a camera. The idea for its algorithm is to eliminate the phase caused by the extended object and reconstruct the point spread function through each lenslet. As a result, the scenario of wavefront sensing from an extended object has been converted to the conventional o…

Composites of resonant dielectric rods: A test of their behavior as metamaterial refractive elements

We report numerical experiments of optical wave propagation in composites of high refractive index dielectric rods at frequencies where their first electric and magnetic Mie resonances are excited. The arrays of these particles have been extensively studied and proposed as non-absorbing and isotropic metamaterials. We show that negative refraction, observed in ordered particle arrays, is due to diffraction and that an effective medium theory yields constitutive parameters that do not reproduce the observations in these composites, whose transmission also depends on the sample shape. This is fu…

Optical left-handed metamaterials made of arrays of upright split-ring pairs

Electromagnetic metamaterials are man-made structures that have novel properties such as a negative refraction index, not attainable in naturally occurring materials. Although negative index materials (NIMs) in microwave frequencies were demonstrated in 2001, it has remained challenging to design NIMs for optical frequencies especially those with both negative permittivity and negative permeability [known as left-handed metamaterials (LHMs)]. Here, by going beyond the traditional concept of the combination of artificial electronic and magnetic meta-atoms to design NIMs, we propose a novel LHM …