Time-bandwidth product of noise-like pulses within the mode-locked regions of a figure-eight fiber laser: theoretical and experimental analysis

Abstract

We present for the first time, to the best of our knowledge, a theoretical and experimental analysis of the time-bandwidth product (TBP) of noise-like pulses (NLPs) within the mode-locked regions of an erbium-doped figure-eight fiber laser (EDFEFL). The tuning of the mode-locked regions was carried out by varying and recording the values of the angle of the polarization controllers in the ring section and in the nonlinear optical loop mirror (NOLM). Within the mode-locked regions, we obtained a large variability of the TBPs. We found that the variability of the temporal profile is greater than that of the spectral profile in all mode-locked regions; for this reason, the TBPs of all mode-locked regions have a behavior proportional to the temporal profile. We also identify the temporal and spectral profiles corresponding to the maximum and minimum TBP. Finally, among all the NLPs within the mode-locked regions, we identify and study the one that is Fourier-transform-limited. We analyze NLPs with a carrier wavelength of 1562 nm with duration in the order of nanoseconds and a repetition rate of 0.9 MHz.