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Picometer Ellipsometer - Configuration - Optical
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Birefringence Modulator

Schematic diagram of the beam path used in the Picometer Ellipsometer




The Picometer Ellipsometer uses the configuration P-BM-S-A (Polariser-Birefringence Modulator-Sample-Analyser). The output from the two signal channels are directly related to Re(r) and Im(r), where r is the fundamental quantity of ellipsometry, being the ratio of the amplitude reflectivities r = rp/rs. Traditionally this ratio is often written

r = tanGreek psi expiGreek capital Delta

so that
Re(r) = tanGreek psi cosGreek capital Delta
Im(r) = tanGreek psi sinGreek capital Delta

The parameter r is a much more direct representation of the ellipsometry signal than the ellipsometric angles Greek psi and Greek capital Delta, which makes results more accessible to interpretation. However, since the Picometer measures both Re(r) and Im(r) simultaneously, the data can always be converted to the traditional notation using Greek psi and Greek capital Delta.

Due to the modular design of the Picometer Ellipsometer, the default P-BM-S-A configuration can be easily configured for many other optical measurements such as measurements of reflectivity, transmission, birefringence, dichroism etc.

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