Filamentation without intensity clamping

P Prem Kiran,Arnaud Couairon,Siva Rama Krishnan,Suman Bagchi,Cord L Arnold,G Ravindra Kumar

doi:10.1364/oe.18.021504

Abstract

We present measurements of the supercontinuum emission (SCE) from ultrashort Ti:Saph laser pulse filamentation in air in a tightly focused geometry. The spectral broadening of SCE indicates that peak intensities exceed the clamping value of a few 10(13) W/cm(2) obtained for filamentation in a loose focusing geometry by at least one order of magnitude. We provide an interpretation for this regime of filamenation without intensity clamping.

Highlights

Ultrashort laser pulse filamentation is widely known as a propagation regime in the form of a narrow intensity peak surrounded by a large energy reservoir allowing both for continuous reconstruction of the hot core by an energy flux from the periphery [1] and for intense laser matter interaction over long distances compared to the Rayleigh length of the peak [2]
We present measurements of the supercontinuum emission (SCE) from ultrashort Ti:Saph laser pulse filamentation in air in a tightly focused geometry
The spectral broadening of SCE indicates that peak intensities exceed the clamping value of a few 1013 W/cm2 obtained for filamentation in a loose focusing geometry by at least one order of magnitude

Summary

Introduction

Ultrashort laser pulse filamentation is widely known as a propagation regime in the form of a narrow intensity peak surrounded by a large energy reservoir allowing both for continuous reconstruction of the hot core by an energy flux from the periphery [1] and for intense laser matter interaction over long distances compared to the Rayleigh length of the peak [2]. [2] which states that the terms of filaments and filamentation denote a dynamic structure with an intense core, that is able to propagate over extended distances much larger than the typical diffraction length while keeping a narrow beam size without the help of any external guiding mechanism This definition includes various filamentation regimes from filaments without plasma channels in loose focusing geometry [7,8,9] to small scale filaments obtained with large numerical apertures [10, 11]. We show that spectral broadening does not fulfil the Liu et al criterion and we model the suppression of intensity clamping when NA is increased

Measurements of Supercontinuum Emission in air

Modeling of filamentation at high numerical apertures

Numerical results

Conclusion