All-Reflection Interferometer for Use as a Fourier-Transform Spectrometer*

This paper describes the design and tests of an all-reflection two-beam interferometer. The unique feature of this interferometer is the use of a combination of three diffraction gratings as a beam splitter. The use of reflection-type diffraction gratings as a beam splitter eliminates the need for transmission elements and thereby extends the applicability of two-beam interferometry to regions of the electromagnetic spectrum such as the vacuum ultraviolet where transmitting beam splitters are not available. A preliminary type of grating beam splitter using a single grating is discussed, and its disadvantages are described. Finally, an interferometer that uses three gratings as a beam splitter and which can function as an all-reflection Fourier-transform spectrometer is described. Interferograms of simple spectra taken with this instrument are presented.