Intracavity Pulse-Duration Measurements in a sub-10 fs Ti:sapphire Laser Oscillator

Recent advances in ultrashort-pulse Ti:sapphire laser technology 1 - 6 have made it possible to routinely generate optical pulses of ~10 fs duration using stable, reliable, and easy-to-use lasers. The Kerr-lens modulation mechanism for mode-locking in these lasers has been identified, 7 and the effect of high-order dispersion on the pulse duration has also been demonstrated. 1 - 4 However, a comprehensive theory covering the operation of these lasers has not been developed, and the ultimate limit of the obtainable pulse-duration is still unclear. We have made measurements demonstrating that sub 10-fs pulses can be produced from a mode-locked laser. We have also compared spectral measurements from the laser with calculations of the dispersion of the laser, and have concluded that even in the case of an 8-9 fs pulse, the primary limitation on even shorter pulse duration is dispersion, and not nonlinear effects. Thus, there remains the prospect of generating even shorter-duration pulses from a Ti:sapphire laser. We have also made measurements of the time-duration and chirp of the optical pulse at various points within the laser cavity. These measurements are also consistent with linear dispersion.