Femtosecond-response, highly third-order nonlinear 4-(N, N-dimethylamino)-3-acetamidonitrobenzene crystal cored fiber

A nonlinear refractive index n2.DAN of a 4-(N, N-dimethylamino)-3-acetamidonitrobenzene (DAN) single-crystal cored fiber of 3.9 mm length and 2.3 μm core radius is evaluated by observing the spectral broadening of a 250 fs pulse due to dispersive self-phase modulation in its fiber and that in a conventional fused-silica fiber. The result shows that the value of the femtosecond-response n2.DAN in the nonabsorbing wavelength region around 625 nm is 1.7×104 times as large as that of the latter’s glass fiber.