We discuss the possibility of using far infrared ellipsometry and synchrotron radiation as a tool in surface and thin-film studies. A portable module that is suitable for measuring the polarization state of reflected radiation between 20 cm(-1) and 800 cm-l is described. A method to deal with the intensity decay after each filling of the storage ring is presented, and polarization and collimation effects in the incoming beam are discussed. The permittivity of GaAs was measured and found to be in excellent agreement with tabulated values. A study was made of vibrational modes in 70 period (GaAs)(n)/(AlxGa1-xAs)(n) superlattice films with n equal to 4, 8, 16, and x = 0.3, 1.0. The confined AlAs-like TO phonon modes in the Al0.3Ga0.7As layers were found to be weakly red-shifted when n increases from 4 to 16. In the (GaAs)(n)/(AlAs)(n) films no shifts could be observed.