The effect of backward injecting wavelength on the mode-locking dynamics of a semiconductor amplifier based fiber laser

Abstract

The wavelength dependent mode-locking performances of a SOAFL under the backward optical injection via a sinusoidal-modulated distributed feedback laser diode (DFBLD) at 1 GHz repetition rate are characterized. The backward optical injection has to be sufficiently high to saturate a SOA and then depletes most of the excited state electrons in the SOA. In order to obtain shorter mode-locking pulsewidth, the DFBLD injecting wavelength should be slightly longer than the peak wavelength of SOA gain to benefit from shorter gain-recovery time and larger modulation depth. As the wavelength of a DFBLD approach the central wavelength of SOA, the shortest pulse was measured via a digital sampling oscilloscope (DSO). The pulses can also be obtained by DFBLD backward injection at 1535 rum in feedback of SOAFL, leading to the optimized pulsewidths of 22.7 ps.