Experimental studies of high order soliton compression effect and gain characteristics in femtosecond laser pulses E-r(3+)-doped fiber amplifier

Seed laser pulses with average power of 146 mu W and pulse duration of 480 fs were amplified to 14.5 mW. The pulse duration was compressed to 260 fs u sing 6 m high concentration E-r(3+)-doped fiber under forward pumping. The amplified signal pulse energy was 0.691 nJ (corresponding to a peak power o f 2 657.7 W) and the repetition rate was 20.84 MHz. Spectrum breakup was ob served simultaneously. The spectrum of pulses amplified by 3 m E-r(3+)-dope d fiber remains a single peak under different pump power. The amplified pul se duration was compressed abnormally with the increasing pump power using the backward pumping; that is, the amplified pulses were compressed with th e increasing pump power under low pump power. When the pump power reached 3 8 mW, the shortest amplified pulse duration was 309 fs. With further increa se in pump power, the amplified pulses began broadening, accompanied by a s ingle peak spectrum under different pump power.