Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Observation of Conical Emission From a Single Self-Trapped Beam



B D. Paul, Marla L. Dowell, Alan Gallagher, J W. Cooper


We report observations of conical emission from a pulsed laser beam with incident laser power, detuning, and beam diameter matched to a range of single, steady-state filaments. The beam thus propagates with nearly constant diameter through 5 cm of strontium (Sr) vapor. Emission angles (θ) are imaged as the height on the input slit of a 1.5 m spectrometer; a charge-coupled device camera in the spectrometer exit plane measures energy as a function of theata} and frequency. Data are reported versus laser-pulse energy, diameter and detuning and the collisional dephasing rate. Sepctrally broad red-detuned cones are observed, but only when the laser beam is predominately self-trapped. As previously observed in experiments where the beam breaks up into multiple filaments, forward emission at the blue-detuned Ragi sideband is much weaker than at the red(cone) sideband. The cone angle is largely independent of the phase velocity of the self-trapped laser beam, which varies from the vapor to the vacuum speed. The efficiency of the cone emission shows incomplete saturation, as well as strong dependence on self-trapped filament parameters.
Physical Review A (Atomic, Molecular and Optical Physics)
No. 6


conical emission, self-focusing


Paul, B. , Dowell, M. , Gallagher, A. and Cooper, J. (1999), Observation of Conical Emission From a Single Self-Trapped Beam, Physical Review A (Atomic, Molecular and Optical Physics) (Accessed June 10, 2023)
Created May 31, 1999, Updated October 12, 2021