Optical anisotropy, order parameter and its critical behavior in temperature-dependent refractive indices of nematic liquid crystals

Optical Anisotropy and Phase Transitions in Lead Halide Perovskites

“…Optical anisotropy or birefringence comes from the dependence of dipole oscillators and refractive index on the crystalline direction, a result of different atomic arrangements along specific orientations of the lattice. Optical anisotropy has been used as a proxy to the order parameter in ferroelectrics, , ferromagnetics, , and nuclear nematicity of liquid crystals . In addition to crystal structures, optical anisotropy may also arise from symmetry breaking in the electronic subsystem, as in the nematic electronic phases related to superconductivity in iron-based superconductors. , Lead halide perovskites (LHPs) have been among the most actively researched materials for optoelectronics and photonics. − In processes based on single crystals, optical propagation depends on the direction and polarization of light if the crystal is optically anisotropic.…”

The experimental average refractive index of liquid crystals and its prediction from the anisotropic indices

“…The traditional method to calculate the apparent average refractive index of an uniaxial liquid crystal n av applies the equation n av = (2n o + n e )/3 (eqn (2)), in which n o and n e are the ordinary and extraordinary refractive indices, respectively. [6][7][8][9] This equation reflects the fact that in uniaxial liquid crystals there are two of three axes of oscillation of light that produce ordinary refractive indices; the third produces an extraordinary refractive index. Eqn (2) hence represents an arithmetic average of the existing refractive indices in an uniaxial liquid crystal.…”

“…For example, in polymer-dispersed liquid crystal devices (PDLC), it is desirable that n av is disparate from the refractive index of the polymer matrix to increase scattering and to ensure a strong contrast between the on and off states of a device. 6 A common method used to combine the anisotropic refractive indices to obtain an apparent average refractive index is given by: [6][7][8][9]…”

“…A common method used to combine the anisotropic refractive indices to obtain an apparent average refractive index is given by: 6–9 in which n i denotes the principal refractive index associated with each axis in the LC material. For uniaxial liquid crystals, two of these axes are equivalent; the equation thus becomes modified to:in which n o and n e are the ordinary and extraordinary refractive indices of the LC, respectively.…”

Thermodynamic and Optical Properties of Mixtures Based on Mesogenic Dysprosium (III) Complex and Nematic Liquid Crystal

“…В формуле (2) n 2  является экстраполяцией температурной зависимости квадрата показателя преломления n 2 is в область температур существования ЖК-фазы. Обоснованность применения соотношения (2) подтверждается многочисленными экспериментальными данными для широкого круга нематических жидких кристаллов [15,16], в которых температурная зависимость n 2  в мезофазе с достаточной степенью точности является продолжением температурной зависимости показателя преломления n 2 is . Зависимости показателей преломления CPDk 3-Ph-F , Dy(CPDk 3-5 ) 3 Bpy 17-17 и их смеси от температуры показаны на рис.…”