Sub-6-fs pulses from a SESAM-assisted Kerr-lens modelocked Ti : sapphire laser: at the frontiers of ultrashort pulse generation

Well-characterized pulses in the two-optical-cycle regime are demonstrated using a Kerr-lens mode-locked (KLM) Ti:sapphire laser and phase-sensitive d iagnostics. The oscillator employs double-chirped mirrors (DCMs) for disper sion compensation, spectral shaping via wavelength-dependent output couplin g, and a semiconductor saturable absorber mirror (SESAM) for reliable opera tion at up to 300 mW output power and with a repetition rate of similar to 90 MHz. In the discussion of the experimental results we emphasize how spec tral shaping can be used most efficiently in the generation of the shortest possible pulse supported by the Ti:sapphire gain bandwidth.