A LAMELLAR GRATING INTERFEROMETER FOR THE FAR-INFRARED

Author Institution: Department of Physics, The Ohio State UniversityA lamellar grating interferometer has been constructed for the primary purpose of investigating the optical properties of solids in the frequency range 2-50 $cm^{-1}$. The interferometer uses a 20 cm $\times$ 20 cm lamellar grating with a 2.5 cm grating constant and 3 cm of travel giving a maximum unapodized resolution of $0.08 cm^{-1}$. Two 50 cm focal length f/1.6 Collimating mirrors are used in a Czerny-Turner arrangement. Light pipe optics feed the light to and from the focal points of the collimating mirrors. The entire assembly is mounted in a vacuum tank which is supported on nitrogen filled bellows for vibration isolation purposes. The properties of different filter materials (fused quartz, epoxy, and plexiglass) will be discussed. The effects of different apodizing functions on selected water vapor lines will also be discussed