What are the advantages of the photoelastic modulator over others forms of polarization modulation? (Part2)
The sensitivity of an ellipsometer is determined by all the different components used. When a PEM is used as the key component, its 50 kHz modulation frequency provides a wide dynamic range without noise. When combined with powerful digital signal averaging the UVISEL phase modulated ellipsometer features an excellent signal to noise ratio from the FUV to NIR.
Fast data acquisition speed
With a modulation frequency of 50 kHz the phase modulated ellipsometer can work with response times as short as 1ms/point, and with good signal : noise ratio. This makes the instrument the ideal system for real-time process control, and to follow dynamic studies and liquid-surface measurements in real-time.
Advanced measurement capability:
Depolarization can occur in case of incoherent reflection, roughness, scattering, inadequate spectral resolution, inhomogeneity. By measuring Is, Ic and Ic' the UVISEL software allows the calculation of the degree of polarization as defined as:
Up to 11 elements of the Mueller matrix can be measured by the UVISEL Phase Modulated Ellipsometer. Mueller matrix measurements are useful when the sample is both depolarizing and anisotropic.