What are the advantages of the photoelastic modulator over others forms of polarization modulation?
Wide spectral range coverage
A major advantage is that a wide spectral range from the FUV to the NIR is covered without the need for several hardware configurations, and without moving any optical elements, the UVISEL provides a continuous and accurate measurement over the wide spectral range from 190 to 2100 nm.
Large acceptance angle
The photoelastic modulator optical element has a large tolerance of the incident angle allowing more simple alignment of the system. As the light beam need not follow the principal axis of a rotating element this is a great advantage when performing measurements in liquid cells, on deposition / etch reactors in-situ.
The UVISEL integrates mirror based optical coupling to the sample providing a microspot capability up to 50 µm over the whole spectral range. Measurements with microspot are useful for the characterization of patterned materials found in semiconductor wafers, display materials, and biosensors. It provides as well several advantages for the analysis of rough layers and devices with transparent substrates.
High Accuracy Measurements for all Values of Psi and Delta
The phase modulated ellipsometer delivers optimum accuracy for all values of Ψ and Δ for any sample by measuring the parameters: