Filamentation and self-compression of multi-mJ fs mid-infrared pulses

Abstract

The physics of strong-field applications, such as filamentation, laser-driven particle acceleration, generation of high harmonics and laser-plasma THz radiation, requires driver laser pulses that are both energetic and extremely short. Moreover, since these applications benefit from extending the oscillation period of the driving electromagnetic field, a longer carrier wavelength is often desirable. Due to the absence of broadband laser gain materials, the common approach for the generation of multi-mJ femtosecond mid-infrared pulses is optical parametric amplification (OPA), and it variation, optical parametric chirped pulse amplification (OPCPA). However, the peak power of the pulses from OPA and OPCPA systems is limited by the maximum energy of pump lasers and restricted by phase-matching bandwidth, as well as the nonlinear phase accumulation in crystals during parametric amplification. Therefore, an external pulse compression, leading to a corresponding peak power increase, is required. This thesis explores the methods of generation and characterization of sub-TW multi-mJ fs mid-IR pulses and investigates their propagation in the filamentation regime. We validate, that high peak-power few-cycle pulses can be generated through a nonlinear soliton-like self-compression in mm-long transparent dielectrics and in ambient air. Furthermore, we show how spectral, temporal, spatial and energetic characteristics of the mid-IR pulse, as well as plasma density and length of the filaments depend on multiple parameters, such as environmental conditions, focusing strength as well as temporal chirp, polarization and energy of the pulses.