Passive harmonic mode-looked soliton fiber laser stabilized using an optically pumped saturable Bragg reflector

We present a new method for generating an equally spaced soliton pulse train from a harmonic passively mode-locked Er/Yb fiber laser. We modulate the saturable loss of the saturable Bragg reflector (SBR) quantum wells by optically pumping it above the bandgap with an external laser amplitude-modulated at a high harmonic of the fundamental repetition rate. This results in a 40-dB suppression of the undesired harmonic modes. Pump-probe measurements show that the reflectivity of the SBR can be changed by 10-4-10-5 producing a modulation in the loss of the cavity, which is more than two orders of magnitude larger than that caused by the self-stabilization mechanism. We implement our approach in a 103.6 MHz repetition race fiber laser running in the 12th harmonic (1.244 GHz) producing ~500-fs soliton pulses