Optic axes

Many of the interesting properties of liquid crystals are a result of chirality or handedness, which is manifest in optical properties by optical activity. For isotropic materials or anisotropic materials viewed along their optic axes, optical activity causes the plane of polarization of propagating light to be rotated by an angle 0. This can be expressed in terms of a difference between refractive indices for left ( ) and right (n ) circularly polarized light ... 

Figures Optical micrograph for a fatigue test at a ax = 60% and R = 0.1, after 240000 cycles...

Figure 1. Schematic of a laser guide adaptive optics system. The laser is pr( jected along or parallel to the telescope ax onto the science object. The deformable mirror can be a separate entity, or can be an adaptive secondary. The light is split among the cameras by dichroics.

The absorption (A ax 402nm, logs 4.71) and emission (A ax 453, 477nm) maxima, fluorescence quantum yields, and the optical energy of 2,5-bis[5-(4,5,6,7-tetrahydrobenzo[b]thien-2-yl)thien-2-yl]-l,3,4-oxadiazole 20 were studied in dichloromethane <1998CEJ2211>. 

Change in the absorption coefficient is found by arranging the measurements and voxel combinations in vector-matrix form as y = Ax where y is the change in absorbance detected at each source-detector pair, A is the so called system matrix derived from Lj and x is the optical parameters of interest, namely the absorption coefficients. 

Examination of the optical spectrum of the filtered purple solution gave a structured absorption band with maxima at 514 and 543 nm. This position is remarkably close (566 nm) to the n-n electronic transition predicted by Davis and Goddard for the parent system H2N=N. As expected for an n-n transition, the position of the absorption maximum is solvent dependent. In dichloromethane solution, A,i ax is 541 nm, in 2-propanol it is 526 nm. The blue shift of 15 nm is completely consistent with the n-n absorptions of isoelectronic carbonyl compounds. 

In practice, phases of the beams are adjustable by tilt angle, q>, of phase retarder plates (glass plates) inserted into the beamlets. The tilt defines the the optical path Ax = nd/cos((p) typically cover-glass shdes with refractive index of n = 1.5 and thickness of d = 180 p.m suffice as variable phase-retarders. 

At the end of this section two tables are presented. The purpose of these tables is to show that, for matching solvents, the main predictions of the theory are fairly well obeyed, viz. that the stress-optical coefficient is independent of molecular weight and concentration. On the other hand, an influence of the solvent is clearly noticed. This means that, according to eq. (2.24), the anisotropy (ax — o ) of the random link is influenced by the solvent molecules. This has first been stated by Frisman, Dadi-vanyan and Dyuzhev (66) (see also Section 5.1.2). 

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