| 摘要 |
An opening (3) is formed on a surface of a metal film (2), a plurality of axes (4, 5, 6, 7) cross each other substantially perpendicularly at the opening (3), a plurality of periodic grooves (8, 9, 10, 11) are provided for respective axes (4, 5, 6, 7), and each of the periodic grooves (8, 9, 10, 11) includes a plurality of grooves (8-n, 9-n, 10-n, and 11-n) substantially perpendicular to the axis for which each periodic groove is provided, and the periodic grooves (8, 9, 10, 11) is positioned point-symmetrically with respect to the opening (3).
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