Femtosecond erbium-doped fiber lasers and a soliton compression technique

The lasing characteristics of an erbium-doped fiber laser with a nonlinear amplifying loop mirror (NALM) were investigated in detail. The NALM was pumped by 1.48 μm InGaAsP laser diodes and an output pulse as short as 123 fs was obtained at 1.56 μm. The 124-fs pulse was shortened to 50 fs by using adiabatic soliton narrowing and high order soliton compression. Soliton narrowing was achieved by amplifying the soliton pulse adiabatically with an erbium-doped fiber amplifier, and a short length of dispersion-flattened fiber was used for soliton compression. Soliton narrowing enabled us to succeed in generating a 98-fs pulse directly from a modified erbium-doped fiber laser.