Linear and nonlinear optical properties of rotaxanes: Novel versatile photonic materials

Linear and nonlinear optical properties of newly synthesized amide based rotaxane films are investigated. The dispersion curves of refractive indices have been characterized. A relatively large anisotropy of refractive indices is observed. The vacuum deposited thin film can be poled by a static electric field. This fact shows some degree of freedom for the mobility of macrocycle with respect to the thread. The induced d₃₃ susceptibility after static electric field polarization at λ=1.064μm is 0.57 pm/V and 3.43 pm/V for rotaxane 1 and 2 respectively. Kinetics of poling and relaxation at different temperatures was studied by in situ SHG technique. From the poling kinetics the characteristic response times of the system were evaluated. Third harmonic generation was measured at 1.064μm and 1.907μm fundamental wavelengths. The electronic part of the third order NLO susceptibility χ⁽³⁾ (-3ω;ω, ω, ω) was found to be (6.4 ± 0.2) ^*10^-13 esu and (4.1 ± 0.8) ^*10^-13 esu at 1.604μm and (6.9 ± 0.4) ^*10^-13 esu and (4.2 ± 0.3) ^*10^-13 esu at 1.907μm for 1 and 2 respectively. Upon UV irradiation a clipping movement induced by a trans-cis isomerization process has been identified.