We have constructed a new facility at the National Institute of Standrds and Technology to measure the index of refraction of transmissive materials in the wavelength range from the visible down to the vacuum ultraviolet (VUV). The interferometric technique uses an etalon of the transmissive material, which is illuminated with synchrotron radiation and the resultant interference fringes are measured using a UV Fourier transform spectrometer (FTS). The refractive index has been measured from 600 nm down to 175 nm and the agreement is better than 1 X 10-5 over the whole spectral range when compared with a traditional goniometric measurement. The uncertainty in the measurement is currently limited by the uncertainty in the thickness measurment of the etalon.
Citation: Journal of Research (NIST JRES) -
Volume: 108 No. 6
NIST Pub Series: Journal of Research (NIST JRES)
Pub Type: NIST Pubs
calcium fluoride, etalon, Fourier transform spectrometer, refractive index, synchrotron, thermal coefficient, ultraviolet