Observing filamentation dynamics with strong field processes

Strong field processes can be used to track complex dynamics in filamentary propagation of ultra-short femtosecond laser pulses. We review latest results on the generation of high-order harmonic radiation generated directly inside femtosecond filaments and elucidate propagation effects through observation of the resulting pulse duration. Few-cycle pulses and their temporal dynamics are measured using stereographic above-threshold-ionization electron spectra. High-order harmonics as a probe for the nonlinear filament dynamics are observed on a wide range of experimental parameters including different generating media and conditions. The observed harmonic radiation supports the generation of isolated attosecond pulses and can be used for high-harmonic spectroscopy of spatiotemporal localized IR pulses interacting with atoms and molecules.