Generation of a Sub-10fs Laser Pulse by a Ring Oscillator with a High Repetition Rate

A compact femtosecond Ti:sapphire ring oscillator composed of chirped mirrors is designed. By accurately optimizing the intra-cavity dispersion and the mode locking range of the ring configuration, we generate laser pulses as short as 7.7fs with a repetition rate as high as 745MHz. The spectrum spans from 660nm to 940nm and the average output power is 480mW under the cw pump laser of 7.5W.