Coherent π-pulse propagation with pulse breakup in an erbium-doped fiber waveguide amplifier

Coherent {π}-pulse propagation with pulse breakup has been observed in an erbium-doped fiber waveguide amplifier. The waveguide was pumped by a 1.48-{μ}m In_1-x{Ga}ₓAsy{P}_{1{{-}}y}$ laser diode. The waveguide had an erbium ion concentration of 8900 ppm and was cooled to 4.2 K. The pulse source was a 1.53-{μ}m mode-locked Er-doped glass laser with a pulse width of 400 ps. A pulse advance of approximately 130 ps was observed between a low-intensity transmitted pulse with a low pump power and an amplified {π} pulse in a 1.5-m-long fiber.