Two-Slit Diffraction Pattern for Gaussian Wave Packets

The complete prediction of diffraction forelectrons passing through one or two slits is obtainedfrom the pure wave propagation governed by theSchrodinger equation. By the further assumption ofelectromagnetic interaction between electrons and slits it isshown that, as already predicted by stochasticelectrodynamics with spin, there exist lateral maxima onthe diffraction pattern corresponding to the edges of the slits.     

Transmission resonances of metallic compound gratings with subwavelength slits

Transmission metallic gratings with subwavelength slits are known to produce enhanced transmitted intensity for certain resonant wavelengths. One of the mechanisms that produce these resonances is the excitation of waveguide modes inside the slits. We show that by adding slits to the period, the transmission maxima are widened and, simultaneously, this generates phase resonances that appear as sharp dips in the transmission response. These resonances are characterized by a significant enhancement of the interior field.     

Single-layer metal nanolenses with tight foci in far-field

In simulations we analyze performance of plasmonic nanolenses made of a single metal layer. We consider the nanolenses in two configurations. In the first, the nanolens is a free-standing silver layer with no hole on the optical axis and double-sided concentric corrugations. In the second, the nanolens has a set of slits instead of grooves. This necessitates integrating the annular metal elements with a dielectric matrix. We examine the following parameters of the nanolenses: film thickness, diameter of an on-axis stop, and lattice constant of slits or double-sided concentric grooves, as well as depth and width of grooves. Due to radially polarized illumination lenses have foci of full widths at half maxima (FWHMs) better than half a wavelength, though foci formed by propagating waves do not decrease beyond the diffraction limit. Due to proper geometry of slits or double-sided grooves lenses have focal lengths of the order of a few wavelengths. Transmission of light through lenses with double-sided narrow grooves reaches 30% while through ones with slits exceeds 80%.     

Apodization to produce a monotonically-decreasing,radially symmetrical,point-spread function

A class of apodized pupil functions is derived which have the property of producing a point-spread function which decreases monotonically with increasing radius. This in turn produces coherent line and edge images which are free of the usual subsidiary diffraction maxima and minima. An example of one of these functions is given, together with the point, coherent line and coherent edge images produced.     

Wachstum von Einkristall-Lamellen in dem engen Raum zwischen parallelen Glasflächen

Single crystal lamina of potassium chlorate and potassium chloride are grown from the solution in the narrow space between two parallel glass surfaces. Electron micrographs are taken at 60 and 80 keV. The monocrystalline structure is demonstrated by the diffraction of a parallel electron beam. The exact thickness of the crystals can be determined from the subsidiary maxima within the Bragg reflections in a convergent beam pattern. Other crystals are under investigation.     

Spin effects in inelastic proton-nucleus scattering

We include the spin-orbit force in the analysis of inelastic proton-nucleus scattering. In the limit of zero-range nuclear forces, very simple results are obtained. To lowest order in the elementary spin-orbit amplitude, the spin-dependent nuclear amplitudes are proportional to the momentum transfer times the spin-independent nuclear amplitudes. Consequently, in the spin-independent cross section the region of the diffractive minima is not significantly affected by the elementary spinorbit amplitudes, whereas the subsidiary maxima are somewhat enhanced.     

Use of a birefringent filter for tuning a synchronously pumped optical parametric oscillator

Design considerations are presented for birefringent filters suitable for use as tuning elements in synchronously pumped optical parametric oscillators. A particular design aspect that is important, since typical gains are rather high, is the adequate suppression of subsidiary transmission maxima, in order to maximize the tuning range. Results are presented on the performance of a picosecond synchronously pumped optical parametric oscillator based on periodically poled lithium niobate with an appropriately designed four-plate birefringent filter. PACS 42.65.Yj; 42.72.Ai     

Influence of the Gaseous Medium on the Spectral Emission of Microplasma Obtained in Evaporating a Sample with the Aid of Laser Radiation

An investigation is made of the influence of air, oxigen, argon, and neon-helium atmosphere on the spatial distribution of the glow of microplasma, obtained in treating a brass sample with laser radiation and excited with the aid of a subsidiary synchronous discharge. The plasma's luminous zone, from which the spectral lines are recorded, extends when the inductance of the discharge circuit is lower and when an inert gaseous medium is used. The maxima of the intensities of the spectral lines with higher excitation energies appear at greater heights from the sample's surface.     

Concave grating miniature spectrometer with an expanded spectral band by using two entrance slits

A new miniature spectrometer with two entrance slits is proposed to expand the spectral band. The proposed spectrometer is designed such that the two entrance slits share the same concave grating and detector array. The two slits are located at different positions such that the spectral range of the same light source incident on the detector array varies greatly between the two slits. Only one of the two slits is illuminated at a given time; as such, the two spectral ranges are sequentially measured. Theoretical calculation and experimentation are conducted to verify the proposed design.     

Experimental sound insulation performance of double frame partitions with slits

In this paper the influence of slits on sound reduction index of double steel frame partitions with and without mineral wool in the cavity was examined. It was shown that the sound insulation of the partition is strongly dependent on the relative position of the slits on each steel frame. As could be expected, the reduction in sound insulation due to slits is lower in partitions without mineral wool in the cavity, since the effect of slits is more important in the case of partitions with high sound insulation.     

Magnetic-flux penetration and critical currents in superconducting strips with slits

We theoretically investigate transport-current-induced magnetic-flux penetration into superconducting strip lines with slits. Even when the individual strips have no bulk pinning, geometrical barriers prevent penetration of magnetic flux into the innermost strips while flux quasistatically penetrates into the outermost slits. The critical current of strip lines with 2N slits at zero applied magnetic field is found to be enhanced by a factor of (N+1)(1/2) above that of a single strip line without slits. Under suitable conditions, a domelike flux distribution due to the geometrical barrier can appear in the individual strips even in the absence of an applied magnetic field.     

Effects of interplay between metal subwavelength slits on extraordinary optical transmission

In this paper we study the extraordinary optical transmission of one-dimensional multi-slits in an ideal metal film.The transmissivity is calculated as a function of various structural parameters.The transmissivity oscillates,with the period being just the light wavelength,as a function of the spacing between slits.As the number of slits increases,the transmissivity varies in one of three ways.It can increase,attenuate,or remain basically unchanged,depending on the spacing between slits.Each way is in an oscillatory manner.The slit interaction responsible for the oscillating transmission strength that depends on slit spacing is the subject of more detailed investigation.The interaction most intuitively manifests as a current distribution in the metal surface between slits.We find that this current is attenuated in an oscillating fashion from the slit corners to the center of the region between two adjacent slits,and we present a mathematical expression for its waveform.     

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.     

Influence of slit width on the electromagnetic transmission of a periodic metallic grating

The light transmittance of a periodic metallic grating with varied slit widths has been investigated. The transmission peaks move to the shorter wavelength direction with an increase in the width of slits while keeping the other parameters unchanged. It was demonstrated that the slit width affects the spectral transmittance of the metal grating significantly. It was also found that the effective refractive index and cavity modes in slits are responsible for this phenomenon. Cavity modes play an important role in extraordinary transmission of the sub-wavelength aperture grating. When a complete resonant mode forms in the slits, a high transmission will appear. A wider slit results in a smaller efficient refractive index and thus affects the cavity mode in the slits. These two elements cause the transmission peaks to move to the shorter wavelength direction with widening of slits. The results obtained here may provide a useful guide to design metallic slit grating devices.     

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.     

Near-field scanner for moving molecules

We have fabricated using electron beam nanolithography a fixed slit near-field optical scanning device which uses near-field fluorimetry to achieve 200 nm spatial resolution of objects moving over the slits. We explore the basic physics of operating narrow slits in the waveguide cutoff mode and present data from the passage of extended double-stranded DNA molecules passing over the slits as a first example of how this device can be used to do ultrahigh spatial resolution mapping of long polymers.     

复合型切缝药包成缝机理及数值模拟实验

 采用爆炸力学、岩石断裂动力学对3种切缝药包进行理论分析表明,复合型切缝药包在切缝方向的剪应力是常规切缝药包的1.59倍左右;采用有限元软件ANSYS10.0/LS-DYNA对其进行数值模拟实验,通过对比3种装药结构的爆炸效果,表明复合型切缝药包在切缝方向的聚能效应最佳;通过对比复合型切缝药包切缝方向和垂直切缝方向的等效塑性应变,得出切缝方向塑性应变峰值是垂直切缝方向的2.93倍左右;通过对比远区围岩压力,得出复合型切缝药包在远区形成的爆炸压力最小,对围岩的损伤程度最小,能量利用最充分。     

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.     

二维阵列狭缝阿达玛光谱仪波长准确度研究

二维阵列狭缝模板是阿达玛编码模板的一种新的设计思想,分析了模板上同列狭缝的加工误差对仪器波长准确度的不利影响,在此基础上,给出了减少同列狭缝高度、垂直光谱维方向上位置不一致性误差对仪器波长准确度影响的方法,以及同列狭缝在光谱维方向上位置不一致导致解码所得谱线产生的光谱偏移量的粗略估计方法,并建立模型进行仿真,计算了当模板上某列狭缝存在宽度、光谱维方向上位置不一致性误差时,解码所得其他各列狭缝谱线分布上测量误差的大小,根据仿真结果可以初步确定模板的加工精度。通过该研究有助于合理设计MEMS(微机电系统)二维阵列狭缝模板,获得对系统误差的有效补偿,提高仪器的波长准确度。     

Microwave transmission of a compound metal grating

An array of subwavelength slits in a metallic substrate supports a series of Fabry-Perot-like resonances, where each harmonic results in a transmission peak. Addition of extra slits per period yields a compound grating with a structure factor associated with the basis. In this study each repeat period is comprised of a central slit flanked by a pair of narrower slits. It supports three resonances for every Fabry-Perot-like solution. New and useful insight into this phenomenon is gained by describing each of the modes in terms of the band structure of diffractively coupled surface waves.