Patent ID: 8877519

Claim:
A chemical sensor element containing a resonator having a first reflector, in which particles of a fine metal structure are arranged two-dimensionally and periodically, counterposed with interposition of a dielectric layer to a second reflector, wherein dimensions of the sensor provide for a resonance wavelength of a resonator, as determined where the entire first reflector is replaced by a metal thin film having the same thickness as the metal fine structure, that is different from a surface plasmon resonance wavelength induced in the metal fine structure and is within ±25% of the plasmon resonance wavelength; and a mode of a surface plasmon resonance excited in the metal fine structure is coupled with a mode of the resonator, as determined where the entire first reflector is replaced by a metal thin film having the same thickness as the metal fine structure, and wherein the resonance wavelength λ1 of the resonator is represented by an equation: mλ 1 =2nL+(φ 1 /2π)λ 1 +(φ 2 /2π)λ 1 , where n is a refractive index of the dielectric layer and L is a thickness of the dielectric layer, λ 1 is the resonance wavelength of the resonator in which the entire of the first reflector is replaced by the metal thin film, φ 1 is a change of phase caused by reflection of light propagating in the dielectric layer by the metal thin film, φ 2 is a change of phase caused by reflection of the light propagating in the dielectric layer by the second reflector, and m is a natural number.