The absorption of ice is dependent upon the direction of the plane of polarization for the near infrared region. Crystals were cut with the optic axis parallel to the surface. Plane polarized radiation was allowed to fall upon the crystal and the per cent transmission determined. The crystal was set in three positions: first, so that the transmitted radiation constituted the ordinary ray, second, so that the transmitted radiation constituted the extraordinary ray, third, so that the incident energy was about equally divided into two rays. For the first position, with a thickness of 5mm, absorption bands were observed at the following wavelengths with the corresponding per cent transmission: .81µ—55 per cent, .92µ—54 per cent 1.06µ—46 per cent, 1.29µ—27 per cent. For the second position the values were: .79µ—93 per cent, .89µ—94 per cent, 1.02µ—93 per cent, 1.26µ—57 per cent. For the third position the transmission curve fell between that of the first and second positions and showed both sets of bands. The region from 1.4µ to 1.7µ was studied by using a specimen 1 mm thick. The position of maximum absorption was located at 1.5µ. The incident energy was unpolarized.
E. K. PLYLER, "THE INFRARED ABSORPTION OF ICE," J. Opt. Soc. Am. 9, 545-549 (1924)