Anisotropy and Emission from Air with Laser Filaments

摘要

Laser laments are extremely interesting entities for their unique characteristics. The high intensity inside the laser laments creates nonlinear effects that are useful in many areas of optics. The laser lamentation is an appealing tool in the standoff spectroscopy for its ability to propagate over long distances while maintains its extreme intensity. However, depletion of energy hinders its propagation over any desired distance. In order to understand the effect of laser laments on the transparent medium that they propagate through, one needs to investigate interaction of the laser laments with the constituents of media. In this work we study the interaction of laser laments with the molecular and atomic gaseous media. We try to separate the molecular and electronic responses of the media. Effect of laser polarization on the response of media is studied for linear and circular polarizations.;Emission from the nitrogen molecules and ions pumped by the laser laments is studied. We show that there are emission in the forward and backward directions from nitrogen gas when it is irradiated by strong pulses that go through lamentation. Effects of laser polarization are also considered by using circular and linear laser pulses.;We propose a technique to enhance the longevity of 800 nm laser laments. By spatially combining the UV laser laments that have low loss and longer propagation distance one can feed the energy reservoir of the IR laser lament through four-wave mixing. We theoretically study this beam combining and show that this scheme is viable and under tunable conditions the energy will ow from the UV lament to the IR lament.