A new ellipsometer its principle, realization and performances

Spectroscopic ellipsometer based on direct measurement of polarization ellipticity

A polarizer-sample-Wollaston prism analyzer ellipsometer is described in which the ellipsometric angles ψ and Δ are determined by direct measurement of the elliptically polarized light reflected from the sample. With the Wollaston prism initially set to transmit p- and s-polarized light, the azimuthal angle P of the polarizer is adjusted until the two beams have equal intensity. This condition yields ψ=±P and ensures that the reflected elliptically polarized light has an azimuthal angle of ±45° and maximum ellipticity. Rotating the Wollaston prism through 45° and adjusting the analyzer azimuth until the two beams again have equal intensity yields the ellipticity that allows Δ to be determined via a simple linear relationship. The errors produced by nonideal components are analyzed. We show that the polarizer dominates these errors but that for most practical purposes, the error in ψ is negligible and the error in Δ may be corrected exactly. A native oxide layer on a silicon substrate was measured at a single wavelength and multiple angles of incidence and spectroscopically at a single angle of incidence. The best fit film thicknesses obtained were in excellent agreement with those determined using a traditional null ellipsometer.

Faraday multipass rotator for use in high accuracy polarimetric or ellipsometric devices

A highly efficient low magnetic field Faraday rotator is presented. A cavity filled with transparent liquid for visible and infrared radiation with a high Verdet coefficient is used. Light travels the cavity several times giving us the advantage of nonreciprocity of the Faraday effect. This cavity is designed in such a way (regarding geometry and the nature of reflecting materials) that it introduces no detectable alteration of the state of polarization of the light, except, under the effect of an applied field, a pure rotation of the polarization plane given by the Faraday law. A rotator using this sort of cavity has potential, in the form of a Faraday modulator, in high precision ellipsometric and polarimetric devices working in the visible and near infrared and using polarization modulation.