Self-focusing effect and multifocus structures of an ultrashort (∼160-fs) pulsed laser beam of ∼1.3-μm wavelength are investigated in several organic liquids. The intensity-dependent self-focusing formation and multifocus structures of the infrared (IR) laser beam were directly observed in a three-photon active fluorescent dye solution cell, in which a high contrast image of the spatial structure of the self-focusing beam can be obtained due to the cubic dependence of the fluorescence intensity on the local IR laser intensity. By combining this dye solution cell with another cell filled with various transparent organic liquids, the contributions of these tested liquids to the observed self-focusing effect are elucidated. The numerical simulations for this type of self-focusing behavior are presented, based on the assumption that the major contribution to the observed self-focusing is the nonlinear refractive-index change of the solvent due to electronic-cloud distortion. The simulation results are in fairly good agreement with the experimental results.
- Multifocus structure
- Three-photon excitation
ASJC Scopus subject areas
- Atomic and Molecular Physics, and Optics
- Condensed Matter Physics
- Electrical and Electronic Engineering