Third-order nonlinear optical properties of regioregular poly(3-hexylthiophene) thin film on quartz glass modified by HMDS and ODTS

The third-order nonlinear optical properties of regioregular poly(3-hexylthiophene) (RR-P3HT) thin films prepared on fused glass substrate were evaluated. The surface modification by hexamethyldisilazane (HMDS) and octadecyltrichlorosilane (ODTS) was performed on the glass substrate to enhance the optical property of the RR-P3HT thin films. The third-order optical susceptibilities chi⁽³⁾ (-3omega; omega, omega, omega) of spin coated P3HT thin films on quartz glass substrate were estimated from optical third-harmonics (TH) intensity measurement using the Maker-fringe method. The orientation, alignment and crystallinity of the RR-P3HT thin films were evaluated using X-ray diffraction and UV-vis absorption spectra. An Nd:YAG laser with a wavelength of 1064 nm, a pulse width of 5 ns and a repetition frequency of 10 Hz was used to evaluate the TH intensity. The effect of surface modification of quartz glass substrate by HMDS and ODTS on the RR-P3HT film structure was also investigated. The third-order nonlinear optical susceptibility (chi⁽³⁾) of RR-P3HT thin films on quartz glass surface modified by ODTS is 1.90 times 10^-8 esu.