High power/high energy pulse generation and propagation

Nonlinear interaction resulting in unusual propagation properties of high power pulsed lasers beams can be exploited for remote and high resolution spectroscopy. Long range interrogation of solids and vapors, for instance by stimulated backward Raman scattering, requires a thorough understanding of the propagation of intense pulses in the atmosphere. Self trapping of femtosecond (in the near IR) and subnanosecond (in the UV) laser pulses into “light filaments” have been proposed as a means to mitigate diffraction. Controlling filamentation over long distances is more difficult than originally anticipated, as recent measurements reveal complex changes in polarization, and changes of index of refraction that cannot be simply explained by the classical Drude model. The latter assumes an electron plasma at equilibrium which does not exist in the fs time scale of the IR filament.