HIGH-ENERGY FEMTOSECOND PULSE AMPLIFICATION IN A QUASI-PHASE-MATCHED PARAMETRIC-AMPLIFIER

A new type of solid-state femtosecond amplifier is demonstrated that i s based on quasi-phase-matched parametric amplification. Such gain med ia are different from conventional solid-state amplifiers in that thei r amplification bandwidths and pump and signal wavelengths can be engi neered. Furthermore, high gain is characteristic of parametric amplifi cation, permitting extraction of high energies without the need to res ort to multiple-pass configurations. We report a parametric chirped pu lse amplification system in which femtosecond pulses from a mode-locke d Er-doped fiber laser system are amplified to 1-mJ energies in a sing le pass by use of a 5-mm-long periodically poled LiNbO3 (PPLN) crystal . This amplifier is pumped by 5-mJ and 0.5-ns pulses at 786 nm, demons trating that limitations associated with a low optical-damage threshol d for long pump pulses can be overcome because of the high nonlinearit y of PPLN and that relatively simple Q-switched lasers can be used wit h such parametric amplifiers. (C) 1998 Optical Society of America.