Cladding-pumped fiber exhibits femtosecond pulse amplification
Researchers from IMRA America (Ann Arbor, MI) and the University of Southhampton (Southhampton, England) have demonstrated that high power levels generated with cladding-pumped fiber lasers can be obtained in the femtosecond-pulse range by employing chirped-pulse amplification.gifrbium served as the sole gain medium in a singly doped double-clad fiber. Previous research on cladding pumping used ytterbium codoping in the fibers, which limited femtosecond performance due to the narrow bandwidths induced by a large phosphate content. The single-doped fibers are phosphate free, and, by eliminating the codopant, pumping efficiency increases.
The power amplifier was pumped with two polarization-multiplexed master oscillator-power amplifier (MOPA) 980-nm diode lasers delivering 1.75 W, with nearly 1.15 W launched into the power amplifier. The power amplifier and a passively modelocked fiber seed oscillator, based on a Kerr-modelocked fiber laser, in conjunction with an all-fiber chirped-pulse amplification system permitted obtaining 380-fs nearly bandwidth-limited pulses with an average power of 260 mW.