Periodic refractive index

Both the amplitude and the direction of the total poling field are functions of position x. The dipole chromophore will align in response to the field Et(x), and a periodic refractive index modulation will be formed due to both molecular anisotropy and the Pockels effect [37], The contribution from molecular anisotropy is an important, sometimes even dominant, mechanism. 

Vasiliev S, Medvedkov O (2000) Long period refractive index fiber gratings properties, applications, and fabrication techniques. Proc SPIE 4082 212-223... 

The spectral response of a holographic PDLC to applied electric fields is shown in Figure 11.27, where white incident hght is used [37]. At 0 V, due to the periodic refractive index, the cell has a high narrow reflection peak. When the applied voltage is increased, the liquid crystal is ahgned toward the layer normal direction. The amplitude of the oscillation of the refractive index decreases and the reflection of the cell also decreases. The drive voltage is approximately equal to the product of the field threshold of the Freedericksz transition of the liquid crystal layer and the cell thickness. 

From our numerical studies, we find that om scheme of 2D localization provide a potential application in atom nano-lithography. With a setup illustrated in Fig. 9, we can lithograph the atoms on a substrate, and fabricate periodic refractive index structures. The numerical simulations of the resulting patterns via 2D atom nano-lithography achieved by our localization method are shown in Fig. 10(a)-(d). The patterns are fabricated on a substrate in the the plane and grow in the z direction (in arbitrary units). In Fig. 10(a), we achieve nanorod arrays disposed on a... 

HPDLCs have periodic refractive index distribution by polymer-rich layer and LC-rich layer, so they can be used as DFB laser cavities. In the DFB laser cavity, the light feedback for lasing modes relies on Bragg scattering by the periodic microstructures [78,79]. The DFB lasing wavelength from the device should satisfy Bragg condition [80]... 

As a result of the spatially periodic intensity function, a spatially periodic refractive index change (i.e., an index grating) is induced. If this index grating is probed by a cw laser, side diffractions in the directions 0, 20, and so on will be generated. This is shown in Figure 9.5 which depicts a typical so-called dynamic grating setup for studying laser-induced nonlinear diffractions. 

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