Origins of Kerr phase and orientational phase in polymer-dispersed liquid crystals

Abstract

Polymer-dispersed liquid crystals (PDLCs) modulate the amplitude and optical phase of light. The optical phase modulation of PDLC can be dissected into two parts: Kerr phase and orientational phase according to the electro-optical (EO) response. We investigated the origins of the Kerr and orientational phases in PDLCs and their connection with the two-step EO response. The Kerr phase is attributed to LC orientation in the center of LC droplets. The orientational phase results from orientation of LC molecules near LC-polymer interfaces. Both phases can be adjusted by varying the droplet size. The two-step EO response in small droplets (<333 nm) is related to the Kerr and orientational phases, and possibly to rotation of point defects. A modified PDLC model considering the Kerr and orientational phases is proposed. Our findings suggest the possibility of versatile photonic devices using pure optical phase modulation.

Effect of Noncovalent Interaction of a Polymer-Dispersed Liquid Crystal for Interferometric Applications over a Range of Low Frequencies

“…The optical response time is sum of the rise time (τ r ) and the decay time (τ d ). , Rise time and decay time are defined as the time required for an amplitude change from 10% to 90% and 90% to 10% of the signal level, respectively, and are given by eqs and : Here, d is the cell gap; ε 0 the is free space permittivity, and Δε is the dielectric anisotropy of the LC. The term W θ is introduced as the polar anchoring strength coefficient, and K eff can be regarded as K 11 , which is the splay elastic constant of LC (it is known that K 11 ∝ Δ n 1.1 ); as the K 11 decreases, anisotropy of LC decreases as well (see splay forms in Figure S5).…”

Optically Isotropic Liquid Crystal Mode Templated by Nanoporous Breath Figure Membrane

“…When we re-estimated the 2D LC fill factor by following the previous reports, the LC volume fill factor of 66.1% corresponded to the 2D LC fill factor of 58% in our work, which was significantly higher than the previously reported achievements (<48% in the 2D LC fill factor) of the OI-NDLCs obtained through the conventional PIPS methods. [46][47][48]…”

Microsecond high‐contrast continuous 2.25π phase modulation based on non‐linear Kerr effect of vertically aligned deformed helix ferroelectric liquid crystal

“…Compared with other EO effects, the non‐linear relationship between electrical field and induced birefringence offers two vital advantages. First, achieving same phase depth within smaller voltage and shorter time 12–14 . Specifically, the common liquid crystals system maintains optical anisotropy regardless of whether the external field is applied or not.…”

“…Specifically, the common liquid crystals system maintains optical anisotropy regardless of whether the external field is applied or not. In Kerr effect devices, the birefringence shows non‐linear voltage dependence, 13,15 with different indices of refraction for the linearly polarized light parallel or perpendicular to the applied field. The difference in index of refraction induced by electric field, 16 is given by where is induced birefringence, is wavelength of incident light, E is the applied electric field, and is Kerr constant.…”