Origin of superenhanced light transmission through two-dimensional subwavelength rectangular hole arrays

Superenhanced light transmission through subwavelength rectangular hole arrays have been reported and some investigations have been made into the physical origin of this phenomenon [K.J. Klein Koerkamp et al., Phys. Rev. Lett. 92, 183901 (2004)]. In our current work, by performing FDTD (finite difference in the time domain) numerical simulations, we demonstrate that mechanism that is different from surface plasmon polaritons set up by the periodicity at the in-plane metal surfaces may account for this superenhanced light transmission. We suggest that for arrays of rectangular holes with small enough width in comparison to the wavelength of the incident light, standing electromagnetic fields can be set up inside the cavity by the surface plasmons on the hole walls with its intensity being substantially enhanced inside the cavity. So resonant cavity-enhanced light transmission is predominant and responsible for its superenhanced light transmission. Rectangular holes behave as Fabry-Pérot resonance cavities except that the frequency of their fundamental modes is restricted by their TM cutoff frequency. However we believe that both localized surface plasmon modes and surface plasmon polaritons set up by the periodicity at the in-plane metal surfaces have their shares in extraordinary optical transmission of rectangular hole arrays especially when the width of the rectangular hole is not small enough and the metal film is not thick enough.     

Transmission of sound through a single vortex

Within a new class of anthracene-like molecules, namely tetrafluoro-acridines, a systematic study of the structural and optical properties of single crystals of a prototypical member, 1,2,3,4-tetrafluoro-7(N,N)dimethyl-amino-acridine, is illustrated. Single crystals were grown by physical vapour transport using an inert gas flow as carrier, starting from a microcrystalline powder of the pure material. The crystal structure, determined by X ray diffraction, points out that the crystals are monoclinic with molecules stacked along the c axis. The results of atomic force microscopy on the ac face of a single crystal, at both low and molecular resolution, are consistent with the X-ray diffraction data. Preliminary results of the optical properties of the single crystal, in the unique configuration accessible due to the peculiar habit of the samples, are discussed.Received: 16 January 2004, Published online: 29 June 2004PACS: 61.66.-f Structure of specific crystalline solids - 68.37.Ps Atomic force microscopy (AFM) - 71.35.Cc Intrinsic properties of excitons; optical absorption spectra     

Transmission of sound through a single vortex

We investigate experimentally the deformation of acoustic wavefronts after crossing of a single, isolated vortex in free space. The incident sound wavelength can be varied in a large domain. We study the wavefronts at variable distance after transmission through the vortex, when the wavelength and the vortex strength are varied. For small wavelength ( , the vortex core size) our results are in very good agreement with predictions and simulations based on geometrical acoustics principles. However, as the sound wavelength increases to value comparable with the vortex diameter, the deformation of the wavefronts show the development of scattering contributions, with characteristics in agreement with recent theoretical and numerical studies.Received: 17 November 2003, Published online: 15 March 2004PACS: 43.28. + h Aeroacoustics and atmospheric sound - 47.32.-y Rotational flow and vorticity     

Quantum transport of a single photon through a subwavelength hole by a single atom

The localization and transport of a photon through a subwavelength hole with the help of a neutral atom are studied. A method proposed and realized in the study is based on the absorption of a photon by a neutral atom directly in front of a subwavelength hole, the flight of the atom through the hole, and photon emission on the other side of the screen. The influence of the interaction of the excited atom flying through the subwavelength channel with the screen material is estimated. The estimate showed that the atomic excitation can be quenched in holes with diameters smaller than 200 nm, which affects the photon transport efficiency.     

Transmission of light through a random small-angle scattering medium

A theory of random small-angle scattering is presented. The photon dispersion partial differential equation is derived and the dispersion coefficient characterizing the medium is introduced. The equation is solved for a spatial impulse. The modulation transfer function and the contrast loss are derived as a funcion of spatial frequency, dispersion coefficient, and object-to-image distance. The limitation on resolution is shown by an indeterminancy relation based on the dispersion coefficient. The dispersion angle (rms value of scattering angle) is calculated as an example.     

Transmission of ultrasound through a single layer of bubbles

We investigate, both experimentally and theoretically, the effect of coupling between resonant scatterers on the transmission coefficient of a model system of isotropic scatterers. The model system consists of a monodisperse layer of bubbles, which exhibit a strong monopole scattering resonance at low ultrasonic frequencies. The layer was a true 2D structure obtained by injecting very monodisperse bubbles (with radius a ∼ 100 μm) into a yield-stress polymer gel. Even for a layer with a low concentration of bubbles (areal fraction, n a ² , of 10-20%, where n is the number of bubbles per unit area), the ultrasonic transmission was found to be significantly reduced by the presence of bubbles (-20 to -50 dB) and showed a sharp minimum at a particular frequency. Interestingly, this frequency did not correspond to the resonance frequency of the individual, isolated bubbles, but depended markedly on the concentration. This frequency shift is an indication of strong coupling between the bubbles. We propose a simple model, based on a self-consistent relation, which takes into account the coupling between the bubbles and gives good agreement with the measured transmission coefficient.     

Enhanced light transmission through a single subwavelength aperture

The optical transmission through a subwavelength aperture in a metal film is strongly enhanced when the incident light is resonant with surface plasmons at the corrugated metal surface surrounding the aperture. Conversely, the aperture acts as a novel probe of the surface plasmons, yielding useful insights for optimizing the transmission enhancement. For the optimal corrugation geometry, a set of concentric circular grooves, three times more light is transmitted through the central subwavelength aperture than directly impinges upon it. This effect is useful in the fabrication of near-field optical devices with extremely high optical throughput.     

Transmission of polarized light through turbid media

The depolarization of light in multiple-scattering media with large (larger than the light wavelength) inhomogeneities is considered. The polarization state of the scattered light is described in the principal-mode approximation. Using the Fokker-Planck model, the polarization and intensity distribution of light are calculated in the vicinity of an inhomogeneity in the shape of an absorbing half-plane. The results of the calculations agree with the experimental data on transmission of light through turbid media.     

Extraordinary light transmission through a metal film perforated by a subwavelength hole array

It is shown that, depending on the incident wave frequency and the system geometry, the extraordinary transmission of light through a metal film perforated by an array of subwavelength holes can be described by one of the three mechanisms: the “transparency window” in the metal, excitation of the Fabry–Perot resonance of a collective mode produced by the hybridization of evanescence modes of the holes and surface plasmons, and excitation of a plasmon on the rear boundary of the film. The excitation of a plasmon resonance on the front boundary of the metal film does not make any substantial contribution to the transmission coefficient, although introduces a contribution to the reflection coefficient.     

Transmission properties of microwave in rectangular waveguide through argon plasma

To study the impact of plasma generated by microwave breakdown on the propagation properties of microwave in high power microwave(HPM) devices, a three-dimensional(3-D) fluid model of argon plasma slab in rectangular waveguide is established and calculated by the finite-difference-time-domain(FDTD) method. A rectangular waveguide with a breakdown chamber filled with argon is set as the physics model, and HPM with frequency of 3–50 GHz propagates through this physics model. The time evolutions of the breakdown process are investigated, the reflection, transmission, and absorption coefficients of HPM are calculated, and the influences of some important parameters, including the thickness of the plasma slab and the microwave frequency on the propagation properties of the microwave are shown. Results of this work can offer theoretical instructions for suppressing the influence of breakdown to the performance of HPM devices, and for the use of microwave breakdown, such as the design of plasma limiter or absorber in HPM devices.     

Modeling of a nanoscale rectangular hole in a real metal

We propose and implement a simple and accurate method to analyze a subwavelength rectangular hole in a real metal and obtain the modal characteristics of its fundamental mode. Our results are found to be in excellent agreement with those reported in the literature, obtained by the effective index method (EIM) and finite-element and finite-difference methods. Unlike the EIM, the present method has no ambiguity in its implementation and is able to predict the major field components also, which may be useful in understanding the extraordinary transmission characteristics of such structures.     

单一亚波长孔径增强透射效应的传输线模型

为了研究亚波长孔径的增强透射效应,把传输线理论引入到了单一亚波长金属孔径的增强光学透射效应中。把金属孔径看成传输线,将电流在传输线上的传输和类Fabry-Pérot腔联系起来;把孔径的出射面看成是传输线的输出端,将出射面的电流看成是一种局域的衰逝电流,电流经传输线在传输线的输出端以天线辐射的形式辐射电磁波。解释了孔径透射的近场分布问题、孔径增强透射峰的位置问题和透射峰位置随金属板厚度的红移问题,得到了与其它理论和实验一致的结果,对开发基于增强透射的亚波长元件具有重要的参考价值。     

Transmission of light through a plane-parallel plate of a two-dimensional resonant photonic crystal

The transmission spectra of two-dimensional resonant photonic crystals of two types have been investigated. Crystals of one type consist of dielectric cylinders forming a square lattice filled by a resonant gas with mercury atoms, and crystals of the other type consist of cylindrical holes filled with a gas and forming a square lattice in a dielectric matrix. It has been established that characteristics of the spectrum of additional transmission arising in the band gap of the photonic crystal can be changed significantly by varying the gas pressure and the angle of incidence. It has been demonstrated that the calculated features in the transmission spectrum of the photonic crystal are stable with respect to a significant increase in the width of the atomic resonance.     

Transmission properties of light through a metallic nanoslit with a defected horizontal nanocavity

Transmission properties of light through a vertical nanoslit milled in a metal film with a defected horizontal nanocavity by introducing a groove-cut nanostrip nearby are investigated. It is observed that the transmittance can be substantially changed in a large range when adjusting the depth of the groove or its position cut in the horizontal nanocavity. Moreover, the variations of the transmittance are given according to different matchings among the magnetic fields at the entrance of the isolated groove, at the entrance of the isolated vertical nanoslit, and at the join position of the horizontal nanocavity to the groove. The obtained results are analyzed physically in detail.     

New type of eigenoscillations and total-transmission resonance through an iris with below-cutoff hole in a rectangular waveguide

The total-transmission phenomenon of the main mode of a rectangular waveguide through a below-cutoff hole in the waveguide shorting before the point of occurrence of the higher-order waveguide modes is found. The effect is due to generation of high-Q eigenoscillations at the evanescent E₁₁ mode and is originated from a specific oscillation formed near a step junction of two waveguides, namely a larger single-mode waveguide and a smaller below-cutoff one. The iris composed of such two junctions is longitudinally symmetric. Thus, a pair of resonances occurs in accordance with the existence of a pair of symmetric and antisymmetric field distributions at the iris. Analogy with the recently found effects in double-periodic gratings with small holes is revealed. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 51, No. 2, pp. 111–121, February 2008.     

Transmission of slow light through photonic crystal waveguide bends

The spectral dependence of the bending loss of cascaded 60 degrees bends in photonic crystal (PhC) waveguides is explored in a slab-type silicon-on-insulator system. An ultralow bending loss of (0.05 +/- 0.03) dB/bend is measured at wavelengths corresponding to the nearly dispersionless transmission regime. In contrast, the PhC bend is found to become completely opaque for wavelengths corresponding to the slow-light regime. A general strategy is presented and experimentally verified to optimize the bend design for improved slow-light transmission.     

Enhanced light transmission through cascaded metal films perforated with periodic hole arrays

We report experimental results on enhanced light transmission through two periodically perforated metal films separated by a layer of dielectric. A perforated metal film (single metallic structure) exhibits extraordinary optical transmission, and when two such perforated metal films are spaced by a dielectric layer (cascaded metallic structure), the transmission is further increased. The maximum transmission of the cascaded metallic structure, which depends on the distance between the two metal films, can be more than 400% greater than that of a corresponding single metallic structure. It is proposed that the coupling of surface plasmon polaritons between the two metal films is involved in the process.     

Translocation of a confined polymer through a hole

Based on an analogy between polymer translocation across a free energy barrier associated with polymer worming through a hole and classical nucleation and growth process, the escape time tau is predicted asymptotically to be N(N/rho)(1/3nu). N is the polymer length, rho is the monomer density prior to escape, and nu is the radius of gyration exponent. Monte Carlo simulation data collected in the high salt limit (nu approximately 3/5) are in agreement with the asymptotic law and provide vivid details of the escape.