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

Abstract
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.