Silver is proposed as a useful metal for thin metal-film subwavelength-grating polarizers in both the terahertz and mid-infrared regions. A triangular Ag-film grating for a terahertz-region polarizer fabricated on a resin substrate showed measured TE-wave losses of higher than 45 dB in the frequency range of 0.5-2.2 THz, while TM-wave losses were lower than 0.75 dB in the range of 0.5-3THz. A triangular double Ag-film grating structure on a thin silicon substrate with an anti-reflection layer on its reverse side was fabricated for the polarizer in the mid-infrared region. Measured TE-wave losses were higher than 27 dB in the wavelength range of 16-21 μm, while the minimum TM-wave loss was 3.5 dB at around the wavelength of 19 μm. Silver films are confirmed to be promising candidates for fabricating high-performance polarizers in the terahertz and mid-infrared regions.

A metal-film subwavelength-grating polarizer with high performance in the terahertz region is presented. The polarizer was obtained by depositing a thin Au film on a resin grating with a triangular cross section duplicated from a metal mold by using the imprinting method. Microstructural parameters were investigated in detail. Measured insertion losses were less than 0.5 dB in the frequency range of 0.5-3 THz, while extinction ratios were 50 dB in the range of 0.5-2.3 THz. The proposed fabrication method is suited to mass production of large-aperture robust polarizers.

The backscattering coefficients observed by synthetic aperture radar (SAR) are influenced by surface geometric roughness obstacles. Using this attributes, spatial distributions of aerodynamic roughness parameter are estimated from the SAR images obtained by the Japanese Earth Resources Satellite (JERS-1). By the method, it is possible to make roughness maps which are very similar to roughness maps derived by the method proposed by Kondo & Yamazawa (1986) which uses the National Land Numerical Information.