Few-cycle light bullets created by femtosecond filaments

We report a generic mechanism of light bullet formation during the filamentation of femtosecond pulses. This mechanism is tested for gaseous and dense media. It allows the production of robust, sub-10 fs structures of light with no post-compression stage. By coupling an infrared pump with a seed beam, tunable pulses with durations down to a few femtoseconds can be generated by parametric processes.