Optical properties of Al, Fe, Ti, Ta, W, and Mo at submillimeter wavelengths

Measurements of the optical constants of metals at submillimeter wavelengths are sparse. We have used a nonresonant cavity to measure, at room temperature, the angle averaged absorptance spectra P(omega) of aluminum, molybdenum, tantalum, titanium, tungsten, and iron in the 30-300-cm(-1) wavenumber region. The real part of the normalized surface impedance spectrum, z(omega) = r(omega) + ix(omega), was determined from P(omega). Measurements were also made on iron from 400 to 4000 cm(-1) using standard reflectance techniques. The r(omega) spectrum was combined with previous measurements by others at higher frequencies and Kramers-Kronig analyses of the resultant combined r(omega) spectra provided epsilon(omega) = epsilon(1)(omega) + iepsilon(2)(omega) and N(omega) = n(omega) + ik(omega).