title: Direct observation of self-focusing with subdiffraction limited resolution using near-field scanning optical microscope
abstract: The self-focusing effect in As2S3 glass has been studied using a near-field scanning optical microscope. Optical images of fine features in the self-focused beam were directly measured at the self-focus with approximately 100 nm spatial resolution. Because of the unusually large nonlinear refractive index at 690 nm, filaments with minimum size of 0.3 &mgr;m were observed in a 1.6 mW beam propagating through the 1.7 &mgr;m thin film. A qualitative analysis of our experimental results is presented. We show that nonparaxiality is responsible for arresting self-focusing, as predicted by recent theories.
authors.affiliation: Department of Physics, Sogang University, 1 Sinsoo-Dong, Mapo-Ku, Seoul, 121-742, Korea.
authors.initials: KB
authors.lastname: Song
authors.initials: J
authors.lastname: Lee
authors.initials: JH
authors.lastname: Kim
authors.initials: K
authors.lastname: Cho
authors.initials: SK
authors.lastname: Kim