The obsolete Lummer-Gehrcke interferometer is reexamined, and it is shown how, with a few simple modifications, this instrument can be used to study the optical properties of thin, solid, dielectric films. In particular, the thickness, the wavelength dispersion, and the absorption spectrum of the film can all be obtained simultaneously. In the case of anisotropic films, the polarization dependence of these parameters is obtained very conveniently. The modified interferometer allows continuous monitoring of the above parameters in situ during growth.
Cardinal Warde, "Lummer-Gehrcke interferometer modified for the spectroscopy of thin dielectric films," Appl. Opt. 15, 2730-2735 (1976)