Compensators, polarized light Elliptic

Figure 17.1.13 Schematic layout of one type of ellipsometer. Linearly polarized light (P) is incident on the sample (5). Reflection produces elliptic polarization (E), which is restored to linear polarization (A ) by the compensator (C). The analyzer (A) is adjusted to achieve extinction. [From R. H. Muller, Adv, Electrochem. Electrochem. Engr., 9, 167 (1973), with permission.]...

The detailed compensation mechanism is explained using Figure 8.26(b). When the unpolarized light from backlight passes through the polarizer (point P), it becomes linearly polarized and its polarization state is located at point T, which deviates fi om the absorption axis of the analyzer (point A). Afterwards, the linearly polarized light (point T) traverses the positive a film, whose position on the Poincare sphere overlaps with point A, and its polarization state is rotated clockwise from point T to point E around the AO axis. Point E is the first intermediate elliptical polarization state. 

In ellipsometry monochromatic light such as from a He-Ne laser, is passed through a polarizer, rotated by passing through a compensator before it impinges on the interface to be studied [142]. The reflected beam will be elliptically polarized and is measured by a polarization analyzer. In null ellipsometry, the polarizer, compensator, and analyzer are rotated to produce maximum extinction. The phase shift between the parallel and perpendicular components A and the ratio of the amplitudes of these components, tan are related to the polarizer and analyzer angles p and a, respectively. The changes in A and when a film is present can be related in an implicit form to the complex index of refraction and thickness of the film. 

A typical experimental ellipsometer is illustrated in Figure 3.7. Monochromatic light, typically from a continuous wave laser, e.g. a He-Ne laser, is plane polarized (the angle of polarization is given by p) and impinges on a surface. A compensator is then used to convert the elliptically polarized reflected beam to a plane polarized beam (with a being the angle of polarization). The analyzer then determines the... 

The principle of the method using the elliptical compensator is based on Eq. (106) expressing intensity I of the light passing through crossed polarizing prisms P and A and two thin anisotropic plates placed between these prisms at azimuths t) and tjk with respect to the polarizer P and introducing the phase differences 5 and 6 respectively )... 

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