| 摘要 |
PROBLEM TO BE SOLVED: To provide a resonant element that has further improved wavelength selectivity while having a polarization separation function.SOLUTION: A resonant element 10A comprises: a dielectric layer 11; a first metallic diffraction grating 12 on a first principal surface 11a; and a second metallic diffraction grating 13 on a second principal surface 11b. The first and second metallic diffraction gratings include multiple first and second metallic members 12a and 13a arrayed in first and second space periods. When widths in a second direction of the first and second metallic members are respectively represented as w1 and w2, the first and second space periods are respectively represented as Λ1 and Λ2, thickness of the dielectric layer is represented as d, thicknesses of the first and second metallic members are respectively represented as d1 and d2 and a refractive index of the dielectric layer is represented as n, w1/Λ1, d1, d, Λ1, w2/Λ2, d2, Λ2 and nsatisfy the following expressions: 0.5≤w1/Λ1, w2/Λ2≤0.9, 10 nm≤d1, d2≤100 nm, 30 nm≤d≤210 nm, 190 nm≤Λ1, Λ2≤400 nm and 1.55≤n≤2.15. |
