Background-Corrected Determination of Optical Properties in the Far Infrared Range up to 1 mm

摘要

The optical properties transmittance and reflectance of materials are defined as the flux of radiation reflectedrnfrom or transmitted through a sample with respect to the incident flux. Usual measurement approaches for thesernquantities follow these definitions and determine the quotient of the reflected or transmitted flux with respect tornthe incident flux. However, in the Mid and Far Infrared Range (MIR and FIR) this approach might easily lead tornwrong results because background radiation sources including the sample itself and temperature gradients insidernthe spectrometer are not correctly considered in this way. The observed deviations are particularly significantrnwhen working with cooled detectors. By carefully temperature stabilizing the spectrometer, by measuring at twornflux levels of incident radiation and by using an appropriate evaluation scheme the transmittance and reflectancerncan be determined in the range from 25 μm up to 1000 μm with largely reduced systematic deviations.