The optical constants of crystal quartz in the far infrared (10–400 cm<sup>-1</sup>) are presented along with the dispersion parameters for the two ordinary-ray bands measured in this study. The asymmetric Fourier-transform method was used for the quantitative measurement of the refractive indices of quartz. The advantages of this method as compared with the channeled-spectrum method usually employed for refractive-index measurements in the far infrared are discussed. The extrapolated, zero-frequency refractive indices of quartz are <i>n</i><sub>0</sub>(0) = 2.106±0.001 and <i>n<sub>e</sub></i>(0) = 2.154±0.001. A pseudocoherence effect is described which permits the measurement of the difference of the principle refractive indices in a birefringent sample without the use of a polarizer.
EDGAR E. RUSSELL and ELY E. BELL, "Measurement of the Optical Constants of Crystal Quartz in the Far Infrared with the Asymmetric Fourier-Transform Method," J. Opt. Soc. Am. 57, 341-348 (1967)