Real time interferometric ellipsometry with optical heterodyne and phase lock-in techniques

In this paper, we have combined a Mach-Zehnder interferometer and an optical heterodyne using an AO modulator to set up an interferometric ellipsometer for measuring the optical properties of metal surfaces. Because there is no moving mechanism, e.g., compensators and quarterwave plates, we can eliminate the errors caused by these elements. By using a phase lock-in technique and computer processing, we can measure parameters Psi and Delta in real time and with great accuracy (where Psi is the amplitude ratio of the P- and S-waves, and Delta is the phase difference in the P- and S-waves).