High-energy self-starting femtosecond Cr4+:Mg2SiO4 oscillator operating at a low repetition rate

We describe a self-starting high-power femtosecond laser based on the Cr4+:Mg2SiO4 crystal that produces 17-nJ pulses of 40-fs duration at 26.5-MHz repetition rate. This low repetition rate is achieved by employment of a one-to-one telescope in the cavity. The pulse energy is five times greater than with a short-resonator laser. To our knowledge, the laser produces the highest energy ever achieved from this type of laser directly from the resonator without cavity dumping or external amplification. We believe that this laser source can be used for many applications, including nonlinear optics, microscopic imaging, and micromachining of silicon and other semiconductor materials, (C) 2001 Optical Society of America.