Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

High Accuracy Ultraviolet Index of Refraction Measurements Using a Fourier Transform Spectrometer



R Gupta, Simon G. Kaplan


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.
Journal of Research (NIST JRES) -
108 No. 6


calcium fluoride, etalon, Fourier transform spectrometer, refractive index, synchrotron, thermal coefficient, ultraviolet


Gupta, R. and Kaplan, S. (2003), High Accuracy Ultraviolet Index of Refraction Measurements Using a Fourier Transform Spectrometer, Journal of Research (NIST JRES), National Institute of Standards and Technology, Gaithersburg, MD (Accessed May 26, 2024)


If you have any questions about this publication or are having problems accessing it, please contact

Created November 1, 2003, Updated February 17, 2017