Liquid crystal birefringence for millimeter wave radar

Measurement of Dielectric Anisotropy of Some Liquid Crystals for Microwave Applications

“…For our measured data, a fairly high correlation coefficient of 0.88 between ∆ε (3 GHz) and ∆n (589nm) was obtained. Similar correlation coefficient (0.8) between ∆ε (30 GHz) and ∆n (589nm) was found for the data measured by Lim et al [14]. For the purpose of normalisation, we plot the dielectric tunability (T%, 3GHz) against ∆n/ne (%, 589nm) ( Figure 5).…”

“…The other set of data was obtained from the work done by Lim K.C. et al at 30GHz [14]. As found in Figure 4, for both the data measured at 3GHz and at 30GHz, the dielectric anisotropy ∆ε (GHz) was larger in the material with higher birefringence (589nm).…”

“…The dielectric tunability, defined as below, was calculated from measured data. Pentyl cyano-biphenyl (K15) is a well known nematic LC, which has been measured in the RF frequency range by various methods [1,3,14]. For comparison purposes, we intended to choose data measured similarly to our method (reflective coaxial method).…”

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

“…Figures 2(c)-(d), to millimeter-or bulkier microwave devices for tunable -delay line, -phase shifter, -wavelength selector and beam steering devices [26][27][28][29][30][31][32][33][34][35][36][37][38][39][40], to name a few. 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.…”

Dielectric anisotropy of nematic liquid crystals loaded with carbon nanotubes in microwave range

“…In comparison with the existing candidate materials such as ferroelectric ceramics, liquid crystals (LC) have drawn attention in recent years because of lower losses at microwave frequencies and comparatively high anisotropy. [1][2][3] LCs can be loaded with various types of nanoparticles for enhanced performance. Anisotropic particles make particularly interesting additives because they may align with the anisotropic host and further enhance its anisotropy.…”