Determination of Optical Constants: A Null-Method

A new kind of ellipsometer is described. Light reflected from a metal surface can be made circular-polarized by simultaneous variation of the azimuth σ of the incident plane-polarized radiation and of the angle of incidence φ. This can be checked by the zero-adjustment of a detector system consisting of a rotating analyser, radiation detector, and lock-in amplifier. The principles of the method are described with special emphasis on the accuracy with which ϵ1 and ϵ2 can be taken. The method has been used to determine the optical constants of gold in the range 1.9 eV ≦ h ω ≦ 4.0 eV without Kramers-Kronig analysis.