title: Kerr self-cleaning of femtosecond-pulsed beams in graded-index multimode fiber.
abstract: We observe a nonlinear spatial self-cleaning process for femtosecond pulses in graded-index (GRIN) multimode fiber (MMF). Pulses with ∼80 fs duration at 1030 nm are launched into GRIN MMF with 62.5 μm core. The near-field beam profile at the output end of the fiber evolves from a speckled pattern to a centered, bell-shaped transverse structure with increasing pulse energy. The experimental observations agree well with numerical simulations, which show that the Kerr nonlinearity underlies the process. This self-cleaning process may find applications in ultrafast pulse generation and beam-combining.
authors: Zhanwei
authors: Z
authors: Liu
authors: Logan G
authors: LG
authors: Wright
authors: Demetrios N
authors: DN
authors: Christodoulides
authors: Frank W
authors: FW
authors: Wise