New design of the variable angle infrared spectroscopic ellipsometer using double Fourier transforms

A new type of incidence-angle-variable infrared spectroscopic ellipsometer working in the 2100-10000 wave number range has been designed and constructed. For the system, the analyzer and polarizer were driven by two microstepping motors having hollow shafts and rotating synchronously with a speed ratio of 2:1, i.e., A = 2P. The incidence angle can be varied from 30° to 90° with an accuracy of 0.01°. The doubled Fourier transforms as both functions of the wave number and the azimuthal angles of the polarizer and analyzer were carried out and integrated in the system. Two sets of ellipsometric parameters measured in the experiment have been used to test the data self-consistency of the system. In data reduction, the error arising from the slight anisotropy of the stray light was corrected. In application, the complex dielectric function of the Au film was measured with a data accuracy better that 1% in the entire spectral range.