Influence of a finite azimuthal energy of surface anchoring on the Fréedericksz transition in droplets of a nematic liquid crystal with a bipolar structure

Holographic Formation of Non-uniform Diffraction Structures by Arbitrary Polarized Recording Beams in Liquid Crystal-photopolymer Compositions

“…Experimental works describing polarization gratings in PDLC (PSLC), such as Reference [36], note that recording should be held at small incident angles. Besides, intensity of formation waves should be high to cross the threshold of Freedericksz transition [35,38]. Thus, described conditions of polarization gratings’ formation correspond to conditions of non-linear phase gratings formation.…”

“…The deformation of the quasi-ellipsoidal droplets is not taken into account in this model. The following expression describes the desired angle [38]:φEfalse(boldr,tfalse)=sans-serifψfalse(boldrfalse)+12⋅arctg[sin[2ϑ0false(boldnormalrfalse)]e2false(boldnormalr,tfalse)+cos[2ϑ0false(boldnormalrfalse)]], where ϑ0false(boldrfalse)=φ0−sans-serifψfalse(boldrfalse)–angle between vectors E and at the initial moment of time (before the recording process); efalse(boldr,tfalse)=Efalse(boldr,tfalse)RΔtrueε¯/K33(5.7δ2+2.1sans-serifλ)–parameter characterizing the effect of an electric field on a bipolar LC droplet; R–droplet radius; δ…”

Compensation of asymmetry of diffraction characteristics of holographic chirped photonic structures in PDLC by the impact of spatially non-uniform electric field

“…Changing of the dielectric constant caused by the impact of external field is due to the reorientation of LC director in the electric field under the action of Fredericks effect [8][9][10]. As in the considered medium the statistical distribution of the LC molecules preferred orientation in the "droplets" is observed [9] we will introduce the corresponding changing of the dielectric constant in the form of statistically averaged tensor:…”

“…LC director orientation changing in each spatial point under the influence of an electric field will be given by the angle of declination from its initial direction. As the considered medium is a set of LC "droplets" suspended in the polymer, to determine the distribution of the "droplets" rotation angle in the sample we will use the theoretical model, developed in [8]:…”

“…-parameter of surface adhesion; a W -azimuth adhesion coefficient; K -Frank's elasticity coefficient;   -effective dielectric anisotropy of bipolar droplet. Critical electric field at which the Fredericks effect will occur is given by [8]:…”