The Effects of Environmental Variables on Ultrashort Laser Pulse Filamentation
Abstract
The proposed research focuses on understanding the interaction of ultrafast laserinducedfilaments with the atmosphere through which" they propagate, in particular theeffect of atmospheric humidity and long-lived photo-generated chemical species such asozone and"" nitrogen oxides on the physical characteristics of the filament. Filamentproperties such as plasma channel density and length, opt""ical energy transmission, andspatio-temporal pulse dynamics will be studied as a function of environmental conditionsat different" laser repetition rates to understand persistent effects (accumulated over manypulses) in a realistic environment. Laser filamentation is based on a dynamic interplaybetween nonlinear focusing and defocusing effects that lead to the propagation of anultrashort laser pulse at very high intensities over long distances compared to theRayleigh range of the laser beam under linear focusing conditions. The high intensitiesachieved in the filament channel lead to excitation and ionization of a fraction of themolecules in t"he filament path. Subsequently, the generated ions and excited species formlong-lived photo-chemical products, such as ozone and ni"trogen oxides. Theconcentration of these species in the vicinity of the filament will build up with anincreasing number of laser p"ulses, so long as the frequency of the pulses is higher thanthe rate at which these chemicals are removed by diffusion or through c""hemical reactions,effectively storing laser energy in chemical bonds. The effect of these processes on thefilamentation dynamics o"f pulses interacting with the modified medium is an importanttopic for any atmospheric filament propagation scheme. A critical asse"ssment of theinteractions between environmental variables such as humidity, changing pressures, andclouds/fog is vital for the tra"nslation of this fledgling technology into practical and usefuldefense tools. In this proposal we lay out a systematic program of research designed toobtain a firm understanding of how water vapor and other trace species present in a realworldenvironment affect" filament propagation dynamics, and how the plume ofpersistent chemical photo-products generated in the filamentation process inter"acts withsubsequent filament pulses and the surrounding environment.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Sep 01, 2017
- Source ID
- N000141712738
Entities
People
- Robert J Levis
Organizations
- Office of Naval Research
- Temple University
- United States Navy