Remote Sensing and Directed Energy Applications of Femtosecond, Terawatt Lasers.

TDC/UDRI will undertake development of a physics based model for the propagation of terawatt, femtosecond laser pulses through the atmosphere. Previous experiments and theoretical results have made it clear that a new approach must be taken in order tohave an unambiguous understanding of this high power ultrashort laser pulse propagation problem in the atmosphere. Simple extensions of the nonlinear Schr¿dinger equation will not suffice to make definite and significant progress on this problem. Theprogram will significantly enhance the simulation and modeling capability for the field of intense ultrashort laser propagation. Our approach is based on rigorous multiple?scales expansions of the vector form of Maxwell's equations and the resultingequations will incorporate important nonlinear effects, as well as, vector fields, non-paraxial, space-time focusing phenomena, and plasma generation. We will not assume radial symmetry and we will incorporate sub-gridding into the computations. Where thecomputations become too memory intense for a single computer we will explore implementing parallel computational methods into our code. The resulting model will provide for verifiable analysis of the details of pulse propagation as a function of initialand boundary conditions, as well as, providing a clear path for Phase II experimental investigation and verification.This effort will result in a model that, when verified by experimentation, will serve as the basis for development of novel, long rangeLIDAR systems. These systems will be used to detect chemical/biological agents at long ranges, as well as provide a means for remote detection of atmospheric chemicals and aerosols for monitoring of pollution. These advanced LIDAR systems may also beused to remotely measure atmospheric turbulence, providing improved, early alert of wind-shear to landing aircraft.