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Organic Materials for Third-Order Nonlinear Optics
Published in Hari Singh Nalwa, Seizo Miyata, Nonlinear Optics of Organic Molecules and Polymers, 2020
Wong and Garito435 developed a relationship between the third-order macroscopic susceptibility and the microscopic molecular susceptibility in the nematic phase and measured THG with different polarization leading to a determination of nonvanishing order parameters P2> and P4> for a nematic liquid-crystal 7V-(p-mcthoxybcnzylidcnc)-p-butylaniline (MBBA). The wedge-maker fringe method was used to demonstrate the simultaneous determination of the order parameters as a function of polarization and temperature. Third-order susceptibility of MBBA was measured as a function of temperature where z axis and x axis are parallel and perpendicular to the nematic director, respectively (Figure 42). These results were in agreement with NMR and Raman scattering studies. Ford et al.456 measured ?3)values of a side-chain liquid-crystal polyacrylate (P-10) containing a (CH2)I0 spacer chain and a 4-dimethylami- nostilbene-4'-carboxylic ester mesogen by the DFWM technique at 532 nm. The P-10 that contains a polarized stilbene side chain showed a resonant ?(3)value of 1.8 X 10~12 esu, a factor 24 times larger than that of carbon disulfide reference. A 90-mm film containing 1.25% DANS in PMMA showed a ?(3)value of 1.1 X 10~n esu.
Photonic Network
Published in Naoaki Yamanaka, High-Performance Backbone Network Technology, 2020
The wavelengths of signal and control lights are λs = 0.9/μm and λc = 0.515 μm, respectively. Although the wavelengths are different, the refractive indices and the nonlinear coefficient for the control light are assumed to be equal to those for the signal light for simplicity. The structure is uniform in the indirection and the nonlinear dielectric region (shaded) has only Kerr-like nonlinearity. Two 3-dB couplers (length L1 = 3000λs) are jointed by parallel straight cores (length L2 = 2200λs). The width of cores, the smallest distance between two cores and the bent angle of cores are d = 4λs, g = 4λs and θ = 0.25°, respectively. The refractive indices of cores and claddings are nf – 1.55 and ns = 1.545, respectively. The refractive index and the nonlinear coefficient of the nonlinear dielectric region are nf and n2 = 10-9 m2/W, respectively. Here, wre assume the nonlinear material to be the liquid crystal MBBA, which has a relatively large nonlinear dielectric coefficient.
Dielectric properties and activation energies of Cu: ZnO dispersed nematic mesogen N-(4-methoxybenzylidene)-4-butylaniline liquid crystal
Published in Journal of Dispersion Science and Technology, 2020
Abhishek Kumar Misra, Pankaj Kumar Tripathi, Kamal Kumar Pandey, Bhupendra Pratap Singh, Rajiv Manohar
The used liquid crystalline material N-(4-methoxy benzylidene)-4-butylaniline (MBBA) having negative dielectric anisotropy (Δε) was purchased by Sigma Aldrich India. MBBA is a wellknown thermotropic mesomorphic material with a transverse dipole moment due to the methoxy group.The mesoscopic dimension of MBBA is 20 Å × 5 Å with dipole moment µMBBA = 2.2 D and activation energy (Ea) 30 kjoule/mole.[24] However, ZnO NP is rod shaped with diameter 12 ∼ 15 nm and length 40 ∼ 80 nm.[23] We have dispersed 8% Cu in ZnO (Cu:ZnO) NPs. Three concentrations (0.5%, 1.0% and 1.5% wt/wt) of NPs in MBBA (N-(4-methoxybenzylidene)-4-butylaniline) are considered.