Temperature dependence of optical constants of silicon for short wavelength FIR laser lines

Using far-infrared (FIR) lasers of 119, 71, 57, and 48 /spl mu/m in wavelength, optical constants (refractive index and absorption coefficient) of a high resistive silicon at 10, 19, and 29/spl deg/C have been measured in order to design a window and a beam splitter of a multi-channel measurement system such as fusion plasma diagnostics. The silicon has a resistivity of about 2.8 k/spl Omega//spl middot/cm. It has been found that the refractive index is sensitive for a change in the temperature. The window and the beam splitter at several temperatures have been designed.