Femtosecond Cr4+: YAG laser with an L-fold cavity operating at a 1.2-GHz repetition rate

Pulses of 55-fs width and 1.2-GHz, repetition rate at 1.52 mu m are generat ed from an L-fold cavity Cr4+:YAG laser by optimization of the lasing-beam mode inside the gain medium. The pulse width is comparable with that obtain ed from a standard Z-fold cavity. The pulses are characterized by a second- harmonic-generation frequency-resolved optical gating method. The pulse sha pe deviates from a sech(2) function because of its broad shoulders. With fu rther miniaturization it should be possible to extend the Cr4+:YAG mode-loc ked operation to multigigahertz rates. (C) 2000 Optical Society of America. OCIS codes: 140.3580, 140.4050, 320.7090, 060.4230.