Femtosecond Cr/sup 4+/:YAG laser optimized for 1.2-GHz repetition rate

Summary form only given. High-repetition-rate Cr/sup 4+/:YAG femtosecond lasers are interesting for possible applications in optical communication system. A promising structure for GHz repetition-rate operation is an L-fold cavity. This type of cavity is simple (few optical elements), compact, highly tunable, and most importantly, it has a wide stability region for Kerr-lens mode-locking, leading to reliable high-repetition-rate operation. The L-fold cavity mode-locked operation has already been demonstrated for the Cr/sup 4+/:YAG laser, but reported pulse widths (75 fs at 0.5 GHz and 125 fs at 1 GHz) are not as narrow as for a standard Z-fold cavity (43 fs). We expect that similar operation should be possible with L-fold cavity with proper optimization.