Experimental study of a passively mode-locked Yb-doped single-polarization microstructure fiber laser

This paper report on passively mode-locked single-polarization large-mode area microstructure fiber laser operating in the purely normal dispersion regime. Stable self-starting mode-locking is obtained using a semiconductor saturable absorber mirror (SESAM). We study the influence of the modulation depth and relaxation time of the SESAM on the mode-locking performances. Different SESAMs with modulation depths varying from 10 to 35% and relaxation times from 500 fs to 9 ps have been used. For all the samples, the laser starts in a Q-switch mode-locking regime. By increasing the pump power, the laser delivers a stable pulse train at a repetition rate of 65 MHz. The highest energies and the shortest pulse durations are obtained using fast SESAMs featuring modulation depths higher than 20%.