Light-induced Fredericks transition in the nematic liquid crystal cell with plasmonic nanoparticles at a cell bounding substrate

The paper presents a theoretical description of the light-induced nematic liquid crystal reorientation in a cell with gold nanoparticles deposited on the surface of one of bounding substrates. It is shown that the surface plasmon resonance in the nanoparticles significantly affects the threshold of the director reorientation. The mathematical model of a surface free-energy density of nematic cell is given, which takes into account the influence of the local electric field on the near-surface nematic layer at the substrate with gold nanoparticles. The threshold intensity of a director orientation instability is calculated and its dependence on the wavelength of incident light and the degree of filling of the surface with gold nanoparticles is analyzed. Comparison of the theoretical calculations with experimental data confirms the full adequacy of the proposed theoretical model.

Figure 1

Geometry of the problem.

Figure 2

Dependence of effective anchoring energy of NLC with the surface on the incident light wavelength $\lambda$. $f_S=0.2$ (1), 0.3 (2), 0.4 (3), 0.5 (4), 0.6 (5), 0.7 (6), and 0.8 (7) (top to bottom).

Figure 3

Calculated and experimental dependencies of the OFT threshold intensity $I_{\mathrm{th}}$ on the cell thickness $L$.

Figure 4

Dependence of the threshold intensity $I_{\text{th}}$ of OFT on the wavelength $\lambda$ of incident light. $f_S=0.2$ (1), 0.3 (2), 0.4 (3), 0.5 (4), 0.6 (5), 0.7 (6), and 0.8 (7) (top to bottom).