Fourier Transform Spectroscopy in the Visible Range

Abstract

We present an undergraduate laboratory that utilizes Fourier spectroscopy with two lasers in the visible range to demonstrate the measurement technique. In addition to teaching an important spectroscopic tool, this laboratory exercise deepens the understanding of Fourier transforms. A Michelson interferometer is used to determine the `unknown' wavelength of a green Helium Neon laser beam by scanning the position of a mirror and comparing the number of observed fringes with that from a known-wavelength red Helium Neon laser beam -the reference beam. The data points are recorded electronically using a photodiode and then transformed into frequency space where the unknown wavelength is calibrated against the known wavelength.