Infrared refractive indices of liquid crystals

Abstract

The refractive indices of E7 liquid-crystal mixture were measured at six visible and two infrared (lambda=1.55 and 10.6 mu m) wavelengths at different temperatures, using Abbe and wedged cell refractometer methods, respectively. The experimental data of the visible wavelengths fit the extended Cauchy equations well. Using the extended Cauchy equations, we can extrapolate the refractive indices of E7 to IR. The extrapolated results almost strike through the measured data. Thus, the extended Cauchy equations can be used to link the visible refractive indices to infrared, where the refractive index measurements are more difficult. (C) 2005 American Institute of Physics

Tunable Metamaterials Made of Graphene-Liquid Crystal Multilayers

“…At λ = 10.6 µm, the ordinary (n o ) and extraordinary (n e ) refractive indices of E7 are determined around 1.5 and 1.7, respectively. As mentioned earlier the n o and n e of the LC are temperature dependent and can be shown as [27,28]:…”

“…The permittivity components of the LC molecules are temperature dependent and the anisotropy of the material can be easily controlled by the electric fields [26][27][28]. Consequently, the optical response of the whole MM structure is modified.…”

“…For E7 nematic LC, T c = 331 K and the fitting parameters at the operating wavelength, λ = 10.6 µm, are obtained as: a = 1.7201, b = 2.25 × 10 −4 (1/K), ( n) 0 = 0.3499 and β = 0.2579 [27]. The imaginary parts of the extraordinary and ordinary refractive indexes at the given wavelength are assumed as κ e = 9.28 × 10 −3 and κ o = 6.75 × 10 −3 , respectively [34].…”

MULTIPLE TIME SCALES OPTICAL NONLINEARITIES OF LIQUID CRYSTALS FOR OPTICAL-TERAHERTZ-MICROWAVE APPLICATIONS (Invited Review)

“…Figure 3 and Table 1. NLC with birefringence approaching unity in the visible regime are now routinely being produced [47,48], and there are increasing efforts to synthesize NLC with large birefringence and low loss in the Terahertz and longer wavelength regime [41][42][43][44][45][46] paralleling the growth in interests in developing tunable electromagnetic devices.…”

“…Nematic liquid crystals are uni-axial, characterized by refractive indices n and the n ⊥ , for light polarization parallel and orthogonal to the director axis, respectively. The magnitude of nematic birefringence Δn = n − n ⊥ is among the largest of all known materials, on the order of 0.2 that holds from the visible through far infrared and well into the microwave regime [1][2][3][41][42][43][44][45][46][47][48], c.f. Figure 3 and Table 1.…”