Electromagnetic enhancement by a single nano-groove in metallic substrate

Zhang, Siwen; Liu, Haitao; Mu, Guoguang

doi:10.1364/josaa.27.001555

Cited by 20 publications

(26 citation statements)

References 27 publications

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“…3(a)]. The electromagnetic enhancement of a bare groove has been studied in detail with a Fabry-Perot model [11]. The model equation of a bare groove is simply (3) with r A and t A replaced by r and t [i.e., removing the HW contribution in (6)].…”

Section: Resultsmentioning

confidence: 99%

Electromagnetic Enhancement by a T-shaped Metallic Nanogroove: Impact of Surface Plasmon Polaritons and Other Surface Waves

Zeng

Liu

2012

IEEE J. Select. Topics Quantum Electron.

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We theoretically investigate the electromagnetic enhancement by a T-shaped nanogroove in a metallic substrate. Compared with a single bare groove without the top trench, a T-shaped groove can achieve a much higher enhancement factor of electric field by more than two times. To explain this improved field enhancement, we build up an intuitive model that explicitly incorporates the mode resonance in the central groove and the excitation and collection of surface waves by the top trench. The model can accurately reproduce the fully vectorial data and thus allows an in-depth analysis of the physics of the field enhancement. Analysis of the model shows that the resonance in the groove can be further enhanced by the excited surface waves that are collected by the top trench and further coupled into the groove. Surface plasmon polariton is shown to be not the unique surface wave that enhances the groove resonance and taking into account another so-called quasi-cylindrical wave will give the full contribution. Our results are helpful for intuitively designing field-enhancement devices that employ surface waves to further enhance the field concentration or resonance.

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Section: Resultsmentioning

confidence: 99%

Electromagnetic Enhancement by a T-shaped Metallic Nanogroove: Impact of Surface Plasmon Polaritons and Other Surface Waves

Zeng

Liu

2012

IEEE J. Select. Topics Quantum Electron.

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“…The assumption that the performance of these types of systems can be modeled on the basis of a single unit has also been followed in a number of other studies [49,51,52]. However, it is well known that collective e↵ects can play an important role in determining the behavior of some types of plasmonic systems [25,[53][54][55][56][57].…”

Section: Model For On-resonance Impedance Matchingmentioning

confidence: 99%

“…For such a dense grating achieving complete absorption requires micron-deep NG channels due to the long SPP wavelength. The case of interest, where the reflectivity extinction occurs for h < 70 nm yielding strong field enhancement [51] and field localization close to the metal surface, is shown in figure 4.7b corresponding to a sparse grating. The distance corresponding to the overlap of the evanescent fields sets lower limit on the region of validity for the analytical model presented here.…”

Section: Model For On-resonance Impedance Matchingmentioning

confidence: 99%

“…It is important to note that no reflected wave exists in the far field, so this approximation is only valid at the metal boundary. On resonance, all the incoming electric field at the metal interface is trapped within the NG [27], and is further amplified due to the NG cavity [51]:…”

Section: Model For On-resonance Impedance Matchingmentioning

confidence: 99%

“…The field enhancement achieved at the mouth of the groove is advantageous for non-linear optical applications such as harmonic generation and multi-photon photoemission [69]. In this way, the NGs serve both as an SPP coupling mechanism, as well as the resonant cavities with strong field enhancement [51] for absorption at the resonant wavelength res .…”

Section: Optical Properties Of Plasmonic Nano Groovesmentioning

confidence: 99%

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Plasmon Enhanced Photoemission

Polyakov

2012

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Next generation ultrabright light sources will operate at megahertz repetition rates with temporal resolution in the attosecond regime. For an X-Ray Free Electron Laser (FEL) to operate at such repetition rate requires a high quantum e ciency (QE) cathode to produce electron bunches of 300 pC per 1.5 µJ incident laser pulse. Semiconductor photocathodes have su cient QE in the ultraviolet (UV) and the visible spectrum, however, they produce picosecond electron pulses due to the electron-phonon scattering. On the other hand, metals have two orders of magnitude less QE, but can produce femtosecond pulses, that are required to form the optimum electron distribution for high e ciency FEL operation. In this work, a novel metallic photocathode design is presented, where a set of nano-cavities is introduced on the metal surface to increase its QE to meet the FEL requirements, while maintaining the fast time response.Photoemission can be broken up into three steps: (1) photon absorption, (2) electron transport to the surface, and (3) crossing the metal-vacuum barrier. The first two steps can be improved by making the metal completely absorbing and by localizing the fields closer to the metal surface, thereby reducing the electron travel distance. Both of these e↵ects can be achieved by coupling the incident light to an electron density wave on the metal surface, represented by a quasi-particle, the Surface Plasmon Polariton (SPP).The photoemission then becomes a process where the photon energy is transferred to an SPP and then to an electron. The dispersion relation for the SPP defines the region of energies where such process can occur. For example, for gold, the maximum SPP energy is 2.4 eV, however, the work function is 5.6 eV, therefore, only a fourth order photoemission process is possible. In such process, four photons excite four plasmons that together excite only one electron. The yield of such non-linear process depends strongly on the light intensity.In this work, the structure consisted of rectangular nano-grooves (NGs) arranged in a subwavelength grating on a metal surface is presented that provides a dramatic increase in the metal's absorption, field localization, and field enhancement. When light is polarized perpendicular to the orientation of the grooves a standing SPP wave is excited along the vertical walls in the NGs, that act as Fabry-Perot resonators. By adjusting the geometry of 2 the NGs and the period of the subwavelength grating the resonance can be fine tuned to a desired position, for example, the laser fundamental wavelength, anywhere from the UV to the near infrared (NIR).Two types of gratings are presented: (a) a gold grating with period of 600 nm, and (b) an aluminum-gold grating with a period of 100 nm; both with resonance at 720 nm. In each case, strong on-resonance absorption was observed, with over 98% for grating (b). Unlike the grating-coupled SPP waves, where the angle is well defined by the momentum matching condition, the resonant NGs allow coupling to the standing modes at a range...

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An All‐Dielectric Metasurface Building Block for the Kerker Effect between Excitons and Nanocavities: Germanium Nanogroove

Huang

Yan

et al. 2017

Advanced Optical Materials

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use noble metallic nanomaterials. [9,10] In recent decades, many groups have brought together plasmonic nanostructures and molecular excitons to form plexcitonic coupling systems. [11] Strong coupling has been observed in many systems, such as silver platelet-J-aggregate nanocomposites, [12] gold nanostar-J-aggregate hybrid systems, [13] and gold nanoshell-J-aggregate complexes. [3] However, plasmonic nanostructures are usually associated with a high level of Joule heating losses at optical frequencies, which limit the efficiency of these coupling systems. [14][15][16] It is also believed that molecular excitons will become instable if the temperature of coupling systems rises, [17] which means that these plexcitonic coupling systems cannot work effectively for a long time. Hence, it is necessary to search for a new type of material to replace the plasmonic nanostructures in these systems.After the demonstration of magnetic dipole resonances of silicon nanospheres in the visible region, [18] all-dielectric materials that could manipulate light at subwavelength scales (similar to metallic materials) were widely studied, especially the high-refractiveindex materials (e.g., silicon, germanium, gallium phosphide, and gallium arsenide). [19][20][21] Simple metallic nanostructures, such as nanospheres or nanorods, can exhibit the electric response only. However, the magnetic response can appear in specially designed metallic nanostructures such as split-ring resonators, U-shape structures, and pairs of nanorods. [22][23][24] Unlike noble metallic materials, all-dielectric materials, even a nanosphere, can support both the electric mode and magnetic mode naturally, which is attributed to the nearly negligible imaginary part of their refractive indices. [19,21,25,26] Because of the magnetic response, a silicon nanoparticle can scatter light asymmetrically as a "Huygens" source. [27] Moreover, directional Fano resonance [28] and magnetic hotspots [29] have been achieved in silicon nanodimers. Therefore, all-dielectric materials may offer an alternative route toward addressing the problems facing plexcitonic coupling systems. Yan et al. generated scattering dark states through the Fano interference between excitons and silicon nanogrooves, [30] and Wang et al. explored resonance coupling in silicon nanosphere-J-aggregate heterostructures and observed a mode Coupling between light and matter has many infusive physical effects and potential applications. Large Rabi splitting energy is achieved in many plasmonic nanostructures; however, these noble metallic materials generally suffer from a high level of Joule heating losses at optical frequencies.As an alternative strategy, all-dielectric materials for manipulating light at the subwavelength scale have attracted enormous interest. However, the understanding of the interactions between all-dielectric nanostructures and molecular excitons remains limited to date. Here, the use of a germanium nanogroove as a new all-dielectric metasurface building block is demonstrated for the ...

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Electromagnetic enhancement by a single nano-groove in metallic substrate

Cited by 20 publications

References 27 publications

Electromagnetic Enhancement by a T-shaped Metallic Nanogroove: Impact of Surface Plasmon Polaritons and Other Surface Waves

Electromagnetic Enhancement by a T-shaped Metallic Nanogroove: Impact of Surface Plasmon Polaritons and Other Surface Waves

Plasmon Enhanced Photoemission

An All‐Dielectric Metasurface Building Block for the Kerker Effect between Excitons and Nanocavities: Germanium Nanogroove

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