Thresholded polarized light

Figure 3 shows thresholded polarized light micrographs of MF-TAG at various crystallization times at 22.5°C. Crystallization curves for AMF, MF-TAG, and MF-DAG by pNMR, turbidity, and PLM-image analysis are shown in Figure 4. MF-TAG crystallized first, followed by AMF and MF-DAG. MF-DAG had the longest induction times determined by pNMR, while by turbidimetry and microscopy, AMF had the longest induction times. Crystallization curves for...

Based on the preceding results, we can say that linearly polarized light from the band-gap absorption region can induce either transitory changes or crystallization transformation in amorphous Sbj Sei alloys. These two phenomena critically depend on exposure, show threshold behavior, and seem to arise from apparently different mechanisms defect states or some kind of structural units given preferential orientation under the action of linearly polarized light. 

The linear stability analysis of the stationary distorted state above the OFT induced by obliquely incident, linearly polarized light was repeated in [12], this time without the numerous approximations used in earlier works, using numerical methods. In addition, dye-doped nematics were considered, for which the threshold for the OFT is much lower and thus permits the experimental realization of a light beam that is much wider than the cell width. For this case, however, absorption also has to be taken into account, which means that the OFT does not happen at p = 1 for perpendicular incidence (see Fig. 16). Taking all of this into account, the exact reorientation profiles for the director were calculated numerically first, and its stability was investigated with respect to spatially periodic perturbations (proportional to exp[i qx + py)]). Then the... 

Figure 11. External field-induced switching as monitored by transmitted polarized light intensity (/) measurements sample A (smeill dots), sample B (medium dots), and sample C (large dots). The arrows indicate switching thresholds as determined from the capacitance measurement (Fig. 10).

The simplest display application of a nematic polymer liquid crystal, using polarized light, involves the splay Freedericksz transition shown in Fig. 5(a) for a material with positive Ac and planar surface alignment. The device is constructed using two polarizers crossed with each other, placed above and below the cell, with their polarization direction at 45° to the director of the planar texture. Above a threshold voltage given by... 

We now consider some quantitative features of the problem. The threshold Ah for the Freedericksz transition with circularly polarized light is given by... 

FIGURE 4.26. The guest-host effect in a nematic Uquid crystal. The orientation of dye molecules and absorption spectra in polarized light (a) no field present (b) the field exceeds the threshold level (P is the polarizer). 

Fig. 7—Electro-optic transfer function of twisted structure. Above threshold, increasing the voltage casuses the structure to lose the ability to rotate the plane of polarized light eventually, the optical behavior of the structure approaches that of a perpendicular home-otropic nematic. The difference (e,), however, is still finite at three times threshold. ...

It is well known that when atoms are excited by a collimated beam of electrons whose energy is at or just above the excitation threshold, the light emitted is strongly polarized. In order to create the atomic polarization necessary for Hanle effect signals using electron bombardment excitation, it is necessary that the electron velocity vector should be perpendicular to the applied magnetic field B. 

---