金属薄膜サブ波長格子から成る偏光子

摘要

金属薄膜から成るサブ波長格子は，高い偏光特性を有することを明らかにしている．数値解析により，テラヘルツ帯において消光比60dB以上の偏光子が得られることを示した．樹脂基板表面に形成したサブ波長格子に厚さ20nmの金属（Au）を被覆した試料を作製し，1-3THzの周波数帯において消光比20dB以上，挿入損失1.5dB以下の特性を得た．本構造は，赤外からテラヘルツの周波数帯において，高消光比，広開口な偏光子として期待できる．%A sub-wavelength thin-metal-film grating is found to have a high polarization-sensitive transmission property. The numerically obtained extinction ratio is as high as more than 60dB in the THz frequency regions. The characteristics were confirmed experimentally by using a 20 nm-thick gold film coated on a resin substrate with a grating. Transmission loss of TE waves was measured to be more than 20dB and TM loss was less than 1.5dB for the frequency region of l-3THz. The structure is promising to obtain a wide-aperture polarizer for the infrared and terahertz wavelength regions.