플라즈몬닉 메타물질을 통한 영차 페브리-페롯 공명투과현상
Observation of the Zeroth-Order Fabry-Perot Resonance
through Plasmonic Metamaterials
Chul-Sik Kee
Nanophotonics Laboratory, Advanced Photonics Research Institute, GIST Email: [email protected]
Metamaterials are new artificial materials to exhibit unusual effective permittivity and permeability in a certain wavelength range.[1-3] They have attracted much attention because they can allow electromagnetic phenomena which are impossible in nature such as negative refraction,[4] perfect lens,[5] optical magnetic resonance [6], and invisible cloaking.[7, 8]
A perfect metal film with a periodic array of holes has been regarded as a plasmonic metamaterial because it has optical properties not to find in a perfect metal film. For example, a perfect metal film with a periodic array of holes can support a surface bound wave that is similar with a surface plasmon of a metal film, although a perfect metal film cannot support the bound wave,[9] and a perfect metal film with a periodic array of cut-through silts can behave as a dielectric layer with a high refractive index.[10]
One of interesting electromagnetic phenomena of a plasmonic metamaterial is the complete transmission through it. The origin of the complete transmission phenomenon has been sought from the effective refractive index of a plasmonic metamaterial. Usually, the effective refractive index has been modeled by the Drude's dielectric constant or retrieved directly from transmission and reflection coefficients.[11-14] The previous studies reported that the complete transmission occurs when the effective index of refraction of a plasmonic matematerial satisfies the impedance matching condition.[13, 14] However, the impedance matching condition just says no reflection but does not provide any insight of resonant properties of a plasmonic metamaterial.
In this talk, we propose a new insight to explain both the complete transmission and the resonant characteristics of a plasmonic metamaterial. We show that the effective index of refraction of a plasmonic metamaterial is zero at the resonant frequency by measuring the phase difference of transmitted electromagnetic waves with and without the metamaterial. We also confirm the zero effective index of refraction of the metamaterial by a THz time-domain spectroscopy (THz-TDS) experiment.[15] The zero index of refraction can allow the zeroth order Fabry-Perot resonance that has been believed to be impossible in nature. We show that the zeroth order Fabry-Perot resonant mode is independent of the thickness of the metamaterial and its wavelength is infinite in the hole. The zeroth order Fabry-Perot resonance also explains well the electromagnetic squeezing and tunneling through narrow holes.
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