Realization of a three-functional-layer negative-index photonic metamaterial

We modify a recently theoretically suggested multilayer negative-index photonic metamaterial design and fabricate corresponding structures with up to three functional layers (seven actual layers) for the first time to our knowledge. Measured transmittance and reflectance spectra agree well with theory.     

Controlling the second harmonic in a phase-matched negative-index metamaterial

Nonlinear metamaterials have been predicted to support new and exciting domains in the manipulation of light, including novel phase-matching schemes for wave mixing. Most notable is the so-called nonlinear-optical mirror, in which a nonlinear negative-index medium emits the generated frequency towards the source of the pump. In this Letter, we experimentally demonstrate the nonlinear-optical mirror effect in a bulk negative-index nonlinear metamaterial, along with two other novel phase-matching configurations, utilizing periodic poling to switch between the three phase-matching domains.     

Broadband 3D isotropic negative-index metamaterial based on fishnet structure

In this paper, we numerically demonstrate a broadband 3D isotropic negative index metamaterial (NIM) at microwave frequency ranges, which is composed of double periodic array metallic fishnet structure (FS) etched on the six sides of a cubic dielectric substrate. The electric and magnetic L-C resonance circuit models are constructed to demonstrate the broadband resonance properties of the proposed 3D metamaterial. The finite integration technology (FIT) simulation and standard S parameters retrieval methods are used to calculate and analyze the negative characteristics, isotropy and polarization of the 3D model. The numerical results show that the negative index bandwidth is about 7 GHz and relative bandwidth can be up nearly to 63%, the negative-index pass band is independent of the polarization of incident waves and is almost the same for different oblique incident angles. Thus, the proposed metamaterial is good candidate as a broad-band 3D isotropic NIMs.     

Enhanced surface plasmon interference lithography from cavity resonance in the grating slits

Surface plasmon interference lithography based on grating diffraction has been studied both theoretically and experimentally in recent years. In this paper, we demonstrate that the cavity resonance in the grating slits can improve the subwavelength interference, not only the intensity but also the uniformity of the pattern. Both the typical lithography structure which merely consists of periodic metallic gratings and the modified structure equipped with a reflection layer are studied. The finite element method has been performed to study the interference pattern. Numerical simulations show that the property of the interference pattern is the optimum when cavity resonance happens. This enhancement can be applied to all the lithography structures which are based on the grating diffraction.     

Dynamic theory of neutron diffraction from a moving grating

A multiwave dynamic theory of diffraction of ultracold neutrons from a moving phase grating has been developed in the approximation of coupled slowly varying amplitudes of wavefunctions. The effect of the velocity, period, and height of grooves of the grating, as well as the spectral angular distribution of the intensity of incident neurons, on the discrete energy spectrum and the intensity of diffraction reflections of various orders has been analyzed.     

Methods to control parameters of a diffraction grating on the surface of lithium niobate electro-optical crystal

Optical transmission and directivity pattern of a tunable diffraction grating that is based on the X-cut lithium niobate electro-optical crystal are studied. It is demonstrated that the intensities in 0 and ±1 diffraction orders decrease by 40% relative to the original level when a voltage of 792 V is applied to electrodes on the crystal. Diffraction orders at angels of ±λ/(2d) and ±3λ/(2d) are demonstrated. The changes of directivity pattern are caused by scattering phase diffraction grating that emerges in the crystal in the presence of the electric field of electrodes and vanishes in the absence of voltage. A hysteresis dependence of the intensity of the zero diffraction order on the voltage is related to the formation of needle-shaped domains with a length of up to 100 μm and a width of up to 10 μm that are oriented perpendicularly to the electrodes. In the vicinity of the domains, the electric field causes rotation of the crystal indicatrix and depolarization and scattering of the transmitted radiation. Under normal conditions, the lifetime of the domains is several weeks when the voltage is switched off and the electrodes are not short-circuited.     

多缝衍射的计算机模拟与演示

利用一个多缝衍射模型模拟光和微观粒子的干涉衍射现象。该模型可演示光的双干涉、ｎ缝衍射及色散现象;也可演示微观粒子的单、双缝衍射,物质波的概率特性及粒子从量行为到经典行为的过渡。     

Design of a highly sensitive surface plasmon resonance sensor using aluminum-based diffraction grating

A highly-sensitive grating-based surface plasmon resonance (SPR) sensor is proposed. The angular interrogation method has been used to study the performance of the sensor, and high sensitivity is obtained if the ?1st diffraction order is used to excite surface plasmon (SP). The sensitivity as well as the width of the SPR curves and reflective amplitude is considered for designing the sensor. Compared with the conventional gold (Au)-based or silver (Ag)-based SPR sensor, it is found that the aluminum (Al)-based sensor has the best performance. The oxidation problem of an Al-based SPR sensor has been addressed by coating it with an ultrathin gold film on the surface. Numerical simulations based on rigorous coupled wave analysis (RCWA) show that the sensitivity of the optimized sensor is 245°/RIU (degree per refractive index unit).     

Echelle diffraction grating demultiplexers with a single diffraction passband

Planar multiplexers based on echelle gratings are very popular devices for optical communication applications. However, the available channel number is restricted by the concept of free spectral range (FSR) due to their high operating diffraction order. Now, we can break the restriction of the FSR concept, and most of wavelengths in the operating passband of echelle grating multiplexers can be used based on a variable diffraction order design. We present the design, fabrication, and characterization of the echelle grating multiplexer with a single diffraction passband based on silica platform.     

Infrared probing of a gaseous diffraction grating

The use of an infrared beam to optically probe an acoustic diffraction grating propagating in air is discussed. With the use of acoustic diffraction gratings for providing beam splitting action for intense infrared radiation, the need for determining the homogeneity of gaseous diffraction gratings has arisen. The study was performed at the Bragg reflection angle using a 10.6 μm wavelength CO₂ laser probe and an acoustic diffraction grating of 0.33 mm spacing.     

双光栅衍射场的干涉效应

双光栅衍射场的干涉效应既具有理论研究价值又具有很实际的应用价值.本文利用波前相因子分析法,推导出了双余弦光栅夫琅禾费衍射场的理论结果;分析了当两个光栅在横向有相对运动时,各级衍射斑光强的变化规律.通过实验观测映证了光强变化与数值计算结果是一致的.这一理论结果是双光栅衍射类实验设计的基础,而这类实验可以用于测量微小振动的振幅和频率.     

Cantor型分形光栅的夫琅禾费衍射特性研究

研究了Cantor型分形光栅的夫琅禾费衍射特性，使我们对分形结构上的衍射问题和特性有一定的了解。     

平面透射光栅的菲涅耳衍射

从标量场的菲涅耳衍射理论出发,研究了球面波入射平面透射光栅的衍射场,导出菲涅耳衍射场的复振幅分布,并得到光栅菲涅耳衍射角的计算公式．结果表明,在理想情况下菲涅耳衍射的每一级衍射波都是一个球面波;在对菲涅耳衍射角进行新的定义后,衍射角的计算仍然可以采用夫琅禾费衍射的光栅方程．     

Test of a diffraction grating neutron interferometer

A practical diffraction grating neutron interferometer has been tested and used to obtain the interference pattern for neutrons with a maximum wavelength of λ = 3.15 Å. Implementation of this principle for very low energy ultra-cold neutrons, permits a substantial expansion of the range of problems which can be solved by neutron interferometry.     

Enhanced transmittance of a dual pass-band metamaterial filter

A broad pass-band metamaterial-based optical filter is experimentally and numerically studied. The designed structure consists of periodically arranged composite metallic arrays and dielectric layer that exhibits transmission responses composed of two flat pass-bands. The coupling of localized surface plasmon (LSP) modes results in the low-frequency pass-band, while the internal surface plasmon polaritons (ISPPs) between the upper and lower metal layers leads to the high-frequency pass-band. Structural parameters (L and R) are experimentally considered from the viewpoint of exploiting their effects on the pass-bands and resonance frequencies. The bandwidths of these pass-bands both can reach to maximums by optimization of these structural parameters. In addition, the two pass-bands can be modulated to be a single pass-band with a bandwidth of 10.7 THz by optimizing L and R simultaneously.     

Radiation of a charge moving over the diffraction grating

The states of a charged particle with a finite free path are determined in the field of a resonant electromagnetic wave. The exact resonance conditions, the modulation and beam instability mechanisms, the charge and current densities (Ohm's law) are obtained for the collisionless beam of resonance particles. Quantum theory of radiation is developed for the resonant adiabatic interaction between a particle and a wave taking into account the interaction with a constant magnetic field induced at the grating surface by the charge and nonresonant waves. The radiation power, the spectrum, and the range of generated frequencies are determined. The results obtained can be used in the plasma and solid-state theories and in electronics.     

环形光栅的菲涅耳衍射

在圆孔的菲涅耳衍射的基础上 ,讨论环形光栅的菲涅耳衍射 ,并给出了计算机仿真结果     

Focussing properties of a holographic plane diffraction grating

A plane holographic diffraction grating is the simplest grating, yet very important component for many optical devices. Very little has been done with regards to its focusing properties and stigmatic conditions. In this paper, we discuss a holographic plane diffraction grating and show that the grating can exhibit focusing properties under some conditions. We also discuss the conditions for zero astigmatism.