Quasi-resonant enhancement of a grazing diffracted wave and deep suppression of specular reflection on shallow metal gratings in terahertz

Tymchenko, Mykhailo; Gavrikov, V. K.; Spevak, I. S.; Kuzmenko, A.A.; Kats, A. V.

doi:10.1063/1.4923419

Cited by 7 publications

(8 citation statements)

References 17 publications

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“…Therefore, the effect of the specular reflection suppression under consideration is attributed to the cumulative (both active and radiative) losses maximum, cf. [8,18]. However, as it is shown below, the point extr   corresponds not only to the specular reflection minimum but results in well expressed maximal nonspecular efficiencies along with the active losses maximum.…”

Section:  mentioning

confidence: 96%

“…Also, Wood discovered one more anomaly related to the unexpectedly high intensity of the grazing outgoing wave [5]. Below the anomalies attributed to the grazing propagating waves are referred to as GA (Grazing Anomaly), see [6][7][8]. Up to now, Wood anomalies are widely discussed due to their perspective role in nanophysics and, particularly, nanophotonics.…”

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confidence: 99%

“…It can be shown that the corresponding quasiresonance behavior is characteristic for the intensity, not for the field amplitude. The method for considering this and other diffraction anomalies analytically was presented in [8], see also a more detailed consideration in [13][14][15].…”

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confidence: 99%

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Reflected energy flux anomaly under grazing incidence: the Brewster angle analogy

2019

The Journal of v. N. Karazin Kharkiv National University, Series "Physics"

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The paper presents thorough theoretical and numerical analysis of the anomalies accompanying light diffraction on periodical structures (gratings). We have developed appropriate theoretical approach allowing to consider strong anomalous effects. Obtained results are presented in the form of analytical expressions for the quntities of interest, both diffracted field amplitudes and the outgoing waves energy fluxes. It is proved existence of the fluxes extrema at the specific grazing angle of incidenceб or wavelength. Namely, the specular reflection can be suppressed even for rather shallow gratings up to approximately total suppression.This effect is accompanied by essential energy redistribution between all outgoing waves depending on the grating profile. It is of essence that the energy maxima exist in all nonspecular diffraction orders at the same point (angle, wavelength) as the minimal specular reflectivity. For small period gratings, such that there do not exist other outgoing waves except the specular one, the reflectance minimum is attended by approximately total absorption of the incident radiation. Thus, we show that the grazing anomaly (GA) can be accompanied by redirection of the incident wave energy into nonspecular diffraction channels and into absorption. The results are applicable in the wide spectral region, from visible and near-infrared to terahertz and high-frequency regions for metals and semiconductors with high permittivity. The anomaly considered is well expressed for high electromagnetic contrast of the adjacent media, say, air and metal or semiconductor. Then the high contrast is due to the high value of the metal/semiconductor dielectric permittivity  ,  1 , and the anomaly corresponds to incidence of TM polarized wave. It is shown that the grazing anomaly (GA) is of rather general type and can take place if other than the specular diffraction order experiencies grazing propagation also. This property follows from the results obtained by strict application of the optical reciprocity theorem to the geometry under consideration. The specific case of harmonic relief grating is discussed in detail. It is demomstrated existence of the characteristic inclination, cr a , of the relief inclinatuion for the grating period comparable with the incident radiation wavelength, 1 cr a  , where  stays for the surface impedance,  1  . The condition cr a a , or greater, corresponds to highly expressed GA. The theoretical results are illustrated by numerical applications to gratings on Cu\vacuum (air) interface in THz region. The results obtained can be simply transferred to the TE polarized waves. For this we have to consider the adjacent media with high contrast magnetic properties, i.e., high value of the magnetic permeability  ,  1 . This case is of high interest for nowaday applications in nanophotonics and metamaterials development. As compared with other anomalies GA is attributed to the resonance-type behaviour of the energy flux, not wave amplitudes, the latter change monotonically within this anomaly contrary to the well known Rayleigh and resonance anomalies, where the wave amplitude experiences fast nonmonotonous dependence on the angle of incidence and wavelength.

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Section:  mentioning

confidence: 96%

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Reflected energy flux anomaly under grazing incidence: the Brewster angle analogy

2019

The Journal of v. N. Karazin Kharkiv National University, Series "Physics"

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“…As far as we know the grazing diffraction anomaly under discussion was not considered earlier. However, in [6,16] one can find the related anomalous effect arising for such parameters of the diffraction problem that some diffracted order corresponds to the grazing wave propagating at the specific grazing angle. The anomaly consists in highly enhanced efficiency of this wave accompanied by deep suppression of the specular reflection.…”

Section: Av Katsmentioning

confidence: 99%

Electromagnetic grazing anomalies. Energy flux extrema

Kats

2019

Low Temperature Physics

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The diffraction of electromagnetic waves at the surface periodic structures accompanied by strong anomalous effects in different diffraction orders is considered in detail for high-contrast interfaces. We restrict discussion by the transverse magnetic polarization of the incident wave (the magnetic field is orthogonal to the plane of incidence) and the simplest geometry when the plane of incidence is orthogonal to the grating grooves. The most attention is devoted to the strong maxima and minima of the energy flux density accompanying specific grazing propagation of some diffraction order. Relation to other anomalies, both Rayleigh and the resonance ones is discussed as well.

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“…In our consideration it is only important that the reflection is associated with "Wood's anomaly" involving the diffracted waves grazing along the star surface (see [11,12,13] and refs in [5]). The grazing diffraction component has the largest amplitude with a large dielectric constant of the reflecting medium and makes the greatest contribution to the ray pressure swinging up the surface.…”

Section: Wood's Anomaly In Mandel'stam-raman Electromagnetic Fieldsmentioning

confidence: 99%

Radiation reflection from star surface reveals the mystery of interpulse shift and appearance of high frequency components in the Crab pulsar

Конторович

Trofymenko

2017

J. Phys.: Conf. Ser.

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Abstract.A new mechanism of radiation emission in the polar gap of a pulsar is discussed. It is based on the curvature radiation which is emitted by positrons moving towards the surface of neutron star along field lines of the inclined magnetic field and reflects from the surface. This mechanism explains the mystery of the interpulse shift and appearance of additional components in the emission of Crab pulsar at high frequencies discovered by Moffett and Hankins twenty years ago. We discuss coherence, energy flux and spectrum of the reflected radiation, appearance and disappearance of the interpulse position shift with the frequency increase. It is also possible that a nonlinear reflection (stimulated scattering) from the star surface is observed in the form of HF components. The frequency drift of these components, discovered by Hankins, Jones and Eilek, is discussed. The nonlinear reflection is associated with "Wood's anomaly" at the diffracted waves grazing along the star surface. Two components can arise due to slow and fast waves which are present in the magnetospheric plasma. The possible scheme of their appearance due to birefringence at the reflection is also proposed. IntroductionTwenty years later after the discovery of interpulse shift and detection of the high frequency (HF) components in the radiation of the Crab pulsar by D Moffet and T Hankins [1], T Hankins, G Jones and J Eilek returned to observation of these phenomena at even higher frequencies [2]. As one of the results, a frequency drift of HF components has been discovered. The detailed analysis of physical results and problems is discussed in the authors' review [3]. The problems of interpulse shift and HF components appearance are marked there as unresolved.The figure (figure 1) from the paper [1] by Moffett and Hankins, 1996 shows that at around 3 GHz there appears a phase shift δ of interpulse (IP) of about 7 degrees comparing to the initial IP positon at lower frequencies. Moreover, two more distinct pulses -high-frequency components [2] -appear at the same frequencies [1,2]. In our preprint [4] (and subsequent papers [5,6]) and in the current work we propose the explanation of these phenomena applying the idea of the radiation reflection from the neutron star surface by returning positrons moving in the polar gap region toward the surface of the star in the inclined magnetic field (figure 2).Presently we consider in detail the curvature radiation (CR) reflected from the pulsar surface.

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Quasi-resonant enhancement of a grazing diffracted wave and deep suppression of specular reflection on shallow metal gratings in terahertz

Abstract: Dual band terahertz waveguiding on a planar metal surface patterned with annular holes Appl. Phys. Lett. 96, 011101 (2010); 10.1063/1.3276545Enhanced zero-order transmission of terahertz radiation pulses through very deep metallic gratings with subwavelength slits

Cited by 7 publications

References 17 publications

Reflected energy flux anomaly under grazing incidence: the Brewster angle analogy

Reflected energy flux anomaly under grazing incidence: the Brewster angle analogy

Electromagnetic grazing anomalies. Energy flux extrema

Radiation reflection from star surface reveals the mystery of interpulse shift and appearance of high frequency components in the Crab pulsar

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