Oscillating-analyzer ellipsometer

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Abstract
The state of polarization of a light beam can be dynamically measured by Fourier analysis of the periodic irradiance variations detected after the beam has passed through an electrooptically oscillating analyzer (OA) composed of an ac-driven optical rotator (Faraday cell) followed by a fixed analyzer. From the dc, fundamental, and second-harmonic components of the photodetector current we obtain the same cosine and sine Fourier coefficients (α and β) as would be measured by a rotating analyzer (RA). An ellipsometer based on this principle, called the oscillating-analyzer ellipsometer (OAE), is proposed with speed and precision comparable to that achieved by the polarization-modulated ellipsometer (PME) of Jasperson et al. Significantly, the OAE does not require a special polarization modulator but uses a Faraday cell instead. Also of importance is the fact that a comprehensive analysis of the effect of systematic errors recently developed for the rotating-analyzer ellipsometer (RAE) applies, in its entirety, to the OAE. Whenever appropriate, the OAE is compared with both the RAE and PME.