Quarter wave plate

This is not the same as circularly polarized light which is obtained by passing linearly polarized light through a quarter-wave plate [53]. The plate produces a superposition of x and y components which are 90° out of phase, i.e. 

Figure 7.25 Set-up for ellipsometry microscopy. Incident linearly polarized light reflects on the surface and becomes eiliptically polarized. The quarter wave plate converts the polarization from elliptical to linear. The analyzer is placed such that it extinguishes all light. If the reflection properties change because a gas is adsorbed, the polarization does not match the setting of the analyzer and light passes through it. Appropriate lenses project an image of the surface onto the CCD camera (adapted from Rotermund [72]).

While this signal is greatly magnified with respect to the polarized CARS signal, which is proportional to, it is still difficult for interpretation. To resolve this problem, an additional quarter-wave plate is introduced into the detection channel. 

In frequency regions where absorption is small the two indices of refraction , and n2 give rise to the phenomenon of double refraction. One of the most common uses for this property is in making wave retarders such as quarter-wave plates incident light linearly polarized with equal x and y field components is phase shifted upon transmission because of the two different phase velocities c/w, and c/n2. An entire field, usually referred to as crystal optics, arises out of this and further applications of crystal anisotropy. 

The plane of vibration of a linearly polarized beam emerging from a quarter-wave plate depends on the phase difference 8 between the interfering ray and is measured by the angle a between the optical axes of the quarter-wave plate and the analyzer ... 

An equally accurate measurement of the phase difference is obtained when a quarter wave plate is introduced between rotor unit and analyzer in the usual way (extinguished between the crossed polarizing prisms). As is well-known, this quarter wave plate transforms the ellipticity of the light-wave emerged from the rotor unit into a rotation according to the simple relation ... 

Fig. 6.8. A Principle of frequency-multiplexed CARS microspectroscopy A narrow-bandwidth pump pulse determines the inherent spectral resolution, while a broad-bandwidth Stokes pulse allows simultaneous detection over a wide range of Raman shifts. The multiplex CARS spectra shown originate from a 70 mM solution of cholesterol in CCI4 (solid line) and the nonresonant background of coverglass (dashed line) at a Raman shift centered at 2900 cm-1. B Energy level diagram for a multiplex CARS process. C Schematic of the multiplex CARS microscope (P polarizer HWP/QWP half/quarter-wave plate BC dichroic beam combiner Obj objective lens F filter A analyzer FM flip mirror L lens D detector S sample). D Measured normalized CARS spectrum of the cholesterol solution. E Maximum entropy method (MEM) phase spectrum (solid line) retrieved from (D) and the error background phase (dashed line) determined by a polynomial fit to those spectral regions without vibrational resonances. F Retrieved Raman response (solid line) calculated from the spectra shown in (E), directly reproducing the independently measured spontaneous Raman response (dashed line) of the same cholesterol sample...

Figure 4.11 Two optical retarders. F fast axis, S slow axis. In both cases the incident beam is polarized under 45°. Left a quarter wave plate retards the slow component of the polarization by 7t/2 and elliptical polarization is achieved. Right a half-wave plate rotates the plane of polarization from 45° to -45°.

Two special retardation devices find wide application in the design of optical po-larimeters. These are the quarter-wave plate with 8 = jc/2 and the half wave plate with 8 = re. The utility of a quarter-wave plate can be demonstrated by observing its effect on... 

The electric vector, A t, of the light generated by the quarter-wave plate is... 

Figure 2.4 The production of circularly polarized light using a quarter-wave plate.

Crossed Polarizers/Quarter-Wave Plate System... 

Figure 8.5 Crossed polarizer/quarter-wave plate system.

The design of a full Mueller matrix polarimeter based on a combination of a (P/RQ) psG and a (RQ/P)psa is shown in Figure 8.11. Here two rotary quarter wave plate... 

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