Investigating the nonlinear optical properties of molten organic materials

The nonlinear absorption of two substituted thiophene compounds containing benzithiazole units was investigated using the Z-scan technique. The experiments were performed using a Nd:YAG las frequency doubled to 532nm with 24ps laser pulses. The samples were prepared as solutions in and as melts by heating above their melting points into the isotropic liquid phase. Both compounds show strong nonlinear absorption under all conditions. Solutions of these materials show little or no linear absorption at the laser wavelength. However, the melts do show significant linear absorption The nonlinear absorption observed has been analyzed using methods for two-photon absorption an two-photon assisted excited state absorption and two-photon absorption cross-sections are reported.