Rochon prism

The spectropolarimeters for the CD and MCD observations in the vaccuum ultraviolet region use prisms and a Rochon prism made of CaF2 or MgF2 234). 

In a similar way, Rochon prisms are made of CaF2 or MgF2 for the vacuum ultraviolet, and quartz for the ultraviolet to visible region. For infrared CD, a wire-grid is used as a polarizer. 

There are numerous polarizing optical components available. Their operation is based on birefringence, polarization at mirrors at the Brewster angle, optical dichroism, etc. Precision achieved with sheet polarizers is inadequate, thus devices like Glan-Thompson, Glan-Foucault or Rochon prisms have to be used. 

A wide variety of other p arizers are available. Most of them, such as Wollaston polarizers and Rochon prism polarizers, s dit the unpolarized light into two beams which DUist then be afially selected. 

Rochon prism An optical device consisting of two quartz prisms the first, cut parallel to the optic axis, receives the light the second, with the optic axis at right angles, transmits the ordinary ray without deviation but the extraordinary ray is deflected and can be absorbed by a screen. The device can be used to produce plane-polarized light and it can also be used with ultraviolet radiation. 

Wollaston prism A type of quartz prism for producing plane-polarized light It deviates the otdin and extraordinary rays in opposite directions by approximately the same amount The Wollaston prism, like the Rochon prism, can be used with ultraviolet radiation. It is named after the inventor William Wollaston (1766-1828). 

In spectral polarimeters. another monochromator is introduced in front of the polarizer. In this type of ORD equipment, the Wollaston prism and polarizer are often combined by pivoting the polarizer to and from in a defined angle. CD equipment is often provided as an additional device for classical absorption spectrometry. With these devices, absorption of left and right circular-polarized light can be measured independently. For this, combinations of Rochon prisms (as polarizers) and Fresnel quartz rhombic prisms (for production of circular-polarized light) are used [34]. Equipment of this type is shown in Figure 22. 

Figure 13.47 Schematic view of the principle setup for RAS. Optical key components are the photoelastic modulator and two polarizers. Usually, a quartz modulator and the Rochon prisms are used. (From [137])...

Figure C3.1.13. Experimentai configuration for far-UV nanosecond CD measurements using a frequency-upconverted Ti sapphire iaser as a probe source. Pj and P2 are Mgp2 Rochon poiarizers at cross orientations. SP is a strained transparent piate with about i ° of iinear birefringence for quasi-nuii eiiipsometric CD detection. Prism PMj and the iris Ij seiect the far-UV fourth hannonic of the argon iaser-pumped Ti-sapphire iaser s near-IR fundamentai output to probe the eiiipticity of the sampie. A second iaser beam at 532 nm is used to pump CD...

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