Optical properties of perforated metal-dielectric heterostructures magnetized in the plane

Physics of the Solid State - The magneto-optical properties of perforated metal-dielectric heterostructures that consist of a metal film perforated with a periodic system of slits and a dielectric...     

基于厚金属狭缝阵列的表面等离子激元光刻

提出一种利用厚金属狭缝阵列耦合激发表面等离子激元制作非周期图形的纳米光刻模型.采用时域有限差分电磁场模拟仿真软件研究了厚金属狭缝阵列中表面等离子激元的激发、模式选择以及光刻胶中的光场分布.结果表明,通过优化厚金属狭缝阵列结构参量和匹配介质参量可有效抑制表面等离子激元在光栅狭缝出口处的发散,增加表面等离子激元的穿透深度,可获得高分辨率的较大曝光深度的周期和非周期纳米图形,可为纳米激光直写技术提供有益的借鉴.     

Surface plasmon resonance transmission filters at 1053nm based on metallic grating with narrow slit

Metallic gratings with narrow slits can lead to special optical properties such as strongly enhancing the transmission and considerably strengthening the polarized effect. A narrow-band filter suitable for application in optical communication is designed by sandwiching a metallic grating between two identical dielectric films. The maximum transmission can reach 96% after optimizing the parameters of films and grating at a central wavelength of 1053 nm. It is the first time, to our knowledge, that such high transmission has been reported since the discovery of the extraordinarily high transmission through periodic holes or slits; moreover, the extremely polarized effect is also found in P mode of this symmetric grating.     

Light passage through a film with subwavelength slits

The effect of anomalously high transmission of an electromagnetic wave through a periodic array of subwavelength slits in a metal film was studied. Results of numerical simulation were compared with theoretical and semi-analytical calculations of anomalous transmission through a silver film. Transmission through a perfectly conductive metal film with subwavelength slits was considered; anomalous transmission through it was detected.     

Reciprocity of Faraday effect in ferrofluid: Comparison with magneto-optical glass

The transmission light intensity method is carried out on a classical platform to study the reciprocity of Faraday effect in water-based Fe₃O₄ ferrofluid and its diluents. Setting the polarization direction of the analyzer at an angle of 45° to that of the polarizer, the switchable DC magnetic field and the alternating magnetic field are imposed to ferrofluid. The ferrofluid film is replaced by magneto-optical glass for contrastive experiments. The results indicate that ferrofluid is different with magneto-optical glass. Even though the direction of magnetic field is reversed, the rotation direction of the polarized light does not change for ferrofluid. The theoretical model of magneto-optical rotation was used to describe the origin of the reciprocity of Faraday effect in ferrofluid and the non-reciprocity in magneto-optical glass. These findings suggest that the magnetic moments of nanoparticles in ferrofluid tend to the same orientation with the magnetic field because of the rotation of particles.     

Magnetic Field Modulated Direct Overwrite with Continuous Wave LaserIrradiation for Magnetic-optic Disks

1.IntroductionAtpresent,therearetwokindsofpracticalrewritableopticalstorage:phase-changeoptiCalandmagneto-opticalstoraged].Magneto-opticaldatastorageisattractiveformassdatastoragebecauseofitshighrecordingdensityandthecontinuouslyincreasingdatatransferrate.DirectoverwriteisapromisingschemetoobtainhighdatatransferratellJ.Magneticfieldmodulation(MFM)andlightintensitymodulation(Lin)arethemajormethodstorealizemagneto--opticaldirectoverwrite[2-8].InLIM,pulsedlaserintensityismodulatedaccordingtot…     

Linear momentum quantization in periodic structures II

Fraunhofer interference of a single particle by a periodic array of scatterers, usually treated with a wave picture, can be fully explained on the basis of linear momentum quantization, as pointed out in a previous study by Van Vliet (1967) [4]. This analysis is now extended to scattering (or passing through slits) involving a finite number N of equidistantly spaced entities comprising the interferometer. The usual intensity probability distribution for W(sinθ) is obtained, noting that total momentum is conserved (as in the Compton effect), while the interferometer is treated as a quantum object—rather than a classical measuring apparatus, as perceived in the Copenhagen interpretation. Various aspects of the ‘orthodox view’ are examined and renounced.     

Marchenko-Ostrovski mappings for periodic Jacobi matrices

We consider 1D periodic Jacobi matrices. The spectrum of this operator is purely absolutely continuous and consists of intervals separated by gaps. We solve the inverse problem (including a characterization) in terms of vertical slits on the quasimomentum domain. Furthermore, we obtain a priori two-sided estimates for vertical slits in terms of Jacobi matrices. Dedicated to the memory of Vladimir Geyler     

Role of surface plasmon polaritons in anomalous transmission of an electromagnetic wave through two arrays with subwavelength slits

The anomalously large transmission of an electromagnetic wave through structures consisting of two periodic arrays of subwavelength slits in films has been investigated. The conditions ensuring zero transmittance of this system have been determined. The role of surface plasmon polaritons in transmission anomalies has been analyzed. An analysis of the systems consisting of three arrays of slits has revealed specific features of the transmittance that are independent of the number of slits. It has been demonstrated that, at a wavelength corresponding to the excitation of a surface plasmon polariton in the gap between two periodic arrays of subwavelength slits, the transmittance is zero (i.e., transmission is suppressed). The investigation has been carried out using numerical simulations with the Fourier modal method.     

N-Slit Diffraction Pattern

The diffraction pattern for particles passingthrough N slits is obtained by a truncation assumptionon the Gaussian wave function when passing the slits andby pure wave propagation governed by the Schrodinger equation with boundaries. The standard limitingsituations give the usual results. In case of a greatnumber of equal and equally separated slits thecalculations are performed by considering also theenergy band structure induced by the periodic boundarygeometry on the initial conditions. The results, whichare qualitatively satisfactory in both cases, do notagree completely in general nor in the limiting cases.     

Flat acoustic lens by acoustic grating with curled slits

We design a flat sub-wavelength lens that can focus acoustic wave. We analytically study the transmission through an acoustic grating with curled slits, which can serve as a material with tunable impedance and refractive index for acoustic waves. The effective parameters rely on the geometry of the slits and are independent of frequency. A flat acoustic focusing lens by such acoustic grating with gradient effective refractive index is designed. The focusing effect is clearly observed in simulations and well predicted by the theory. We demonstrate that despite the large impedance mismatch between the acoustic lens and the matrix, the intensity at the focal point is still high due to Fabry–Perot resonance.     

介质覆层下金属周期结构变化对TE波异常透射特性的影响

根据金属光栅结构变化对TE波异常透射特性影响的研究需要,建立了相应的模型。应用时域有限差分(FDTD)方法分别计算了单缝结构、多缝结构、不同宽度和不同周期等结构下的透射分布特征。研究发现添加凹槽会对金属表面能量的传递起阻碍作用。透射频域宽度随薄膜宽度增加而增加。随着狭缝宽度的增加,透射率分布曲线包络线趋于平坦,主透射峰短波长侧透射曲线分布基本不变,而主透射峰及其长波长侧的透射曲线分布变宽。这说明宽度的变化影响了表面共振模式,从而影响透射的分布。单个狭缝的透射与多周期结构相比,透射率曲线几乎重合,表明狭缝对表面模式没有调制作用,各狭缝的透射相对独立。     

Nonreciprocal extraordinary optical transmission through subwavelength slits in metallic film

We demonstrate the phenomenon of nonreciprocal extraordinary optical transmission (NEOT) through metallic film with slits on the substrate of magneto-optical materials. Under uniformly magnetization, the system can show nonreciprocal transmission at near-IR frequency range. With a properly designed structure, the nonreciprocity can be as high as 57.6%. Numerical evidence shows that the nonreciprocal performance is sensitive to the incidence angle, as well as to the thickness of the substrate.     

A cold 87Rb atomic beam

We demonstrate an experimental setup for the production of a beam source of cold ⁸⁷Rb atoms. The atoms are extracted from a trapped cold atomic cloud in an unbalanced three-dimensional magneto-optical trap. Via a radiation pressure difference generated by a specially designed leak tunnel along one trapping laser beam, the atoms are pushed out continuously with low velocities and a high flux. The most-probable velocity in the beam is varied from 9 m/s to 19 m/s by varying the detuning of the trapping laser beams in the magneto-optical trap and the flux can be tuned up to 4×10⁹ s^-1 by increasing the intensity of the trapping beams. We also present a simple model for describing the dependence of the beam performance on the magneto-optical trap trapping laser intensity and the detuning.     

Non-resonant magneto-optical effects in cold atoms

We report a novel nonresonant magneto-optical effect in cold atoms and present the optimized parameters of the biased magnetic field, the incident probe light intensity, and the probe detuning to obtain the maximal signal of the magneto-optical rotation. This detection scheme may further improve the stability of the cold atom clock.     

Experimental and calculated research on a large band gap constituting of tubes with periodic narrow slits

A new band gap structure composed of a square array of parallel steel tubes with narrow slits is presented. The propagation of acoustic waves in a two-dimensional composite medium constituted of slit tubes in air is investigated both theoretically and experimentally. The band gap is calculated with the finite element method in which the acoustic-solid coupling is taken into account. The transmissions of the band system with both different single-width narrow slits and multi-width narrow slits are analyzed. Experimental measurements show that the transmission through an array of slit tubes with periodic narrow slits drops to noise level throughout frequency interval in good agreement with the calculated forbidden band. The large band gap and low starting frequency is obtained by arranging different width of slits embedded in the tubes. The experiments and theoretical results show that this new band gap structure has an especial character based on the resonant cavity playing an important role on the band gap besides the traditional Bragg interference.     

Waveguide resonance of subwavelength metallic slits

The transmission characteristics of a metallic film with subwavelength periodic slits are investigated by using the two-dimensional finite-difference time-domain method (2D-FDTD). Two models are constructed to show the dependance of the transmission spectrum on the slit structure. A sandwiched structure is used to exhibit the contribution of the metallic wall inside slits to the extraordinary high transmission. And a filled slit structure is employed to reflect the relation between the average refractive index inside the slits and the transmission spectrum of the structure. The transmission characteristics of two structures can be explained well with the waveguide resonance theory.     

The optical transmission characteristics through gold nanoslit arrays embedded in nonlinear medium

We present the numerical investigation of the optical transmission through a periodic gold nanoslit array embedded in the Kerr type nonlinear medium by using a developed two-dimensional Finite Different Time Domain (FDTD) method. The enhanced transmission in the nonlinear structure is attributed to the collaboration of the surface plasmon resonance and the localized waveguide resonance. We show that, in a certain intensity range, with the increase of the incident intensity, the transmission resonance peaks redshift obviously, and peak values decrease firstly and then increase; with the gold film thickness and the embedded depth becoming larger, transmission resonance peaks of both types redshift significantly, and the peak number, peak value and the half peak width change obviously. The electric fields distributions for different embedded depths of the gold slits at various resonance wavelengths are simulated to illuminate the underlying physical mechanisms. It is expected that these results obtained here will help to design nonlinear subwavelength metallic grating devices.     

Magnetization reversal of microsized Fe elliptic rings

We report on the magnetization reversal of elliptic ring patterns lithographically prepared from Fe films. The elliptic rings in four different arrays are all of the same size , but their geometry is disturbed by introducing an increasing number of slits into the rings. The magnetization reversal is studied by regular longitudinal vector magneto-optical Kerr effect in specular geometry as well as in Bragg geometry, using the diffraction spots from the grating for hysteresis measurements. The measurements are compared with the results of micromagnetic simulation, which allow a detailed interpretation of the experimental data. We find that the remagnetization process in an external magnetic field is characterized by single-step switching or double switching depending on the geometry of the structure.