PT Unknown AU Loudkov, D Tong, CE Marrone, DP Ryabchun, S Paine, SN Blundell, R TI Transmission measurements of infrared filters for low-noise terahertz receiver applications SE Proc. 16[super:th] Int. Symp. Space Terahertz Technol. PY 2005 BP 354 EP 357 DE FTS; Zitex; alkali halide; crystalline quartz; Parylene; polyethylene; IR filters; transmission; THz applications AB Infrared (IR) filters are very important to the efficient operation of cryogenic receivers. Usually, such filters are mounted on the radiation shield of the cryostat to reduce the heat load to the 4 K stage. Insufficient filtering may cause the temperature of the mixing element in a receiver to be excessively warm, leading to degradation in sensitivity. These filters should be effective in blocking the room temperature IR radiation from outside the cryostat, yet should be transparent across the desired signal frequency band. In the Terahertz frequency range, which is close to the infrared, it is difficult to find an inexpensive low- loss material that can provide the required IR blocking capacity. We present transmission measurements, made using a Fourier Transform Spectrometer (FTS), of a number of potential infrared filters between 0.4 and 1.6 THz. The filters tested include the widely-used, Teflon-based, Zitex-A and Zitex-G films, alkali halide based infrared filter, and crystalline quartz coated with Parylene, and polyethylene films. ER