CW-pumped polarization-maintaining Brillouin fiber ring laser: II. Active mode-locking by phase modulation

Stimulated Brillouin backscattering in a cw-pumped long optical polarizationmaintaining fiber ring cavity excites spontaneous stable mode-locking. But the shortest pulses allowed by the Brillouin gain bandwidth imply an active modelocking, which we have achieved by using a phase modulator inside the ring. The experiment is carried out in the infrared at 1.319 μm, and in narrow frequency domains, close to N integer multiples of the ring FSR, we observe two type of mode-locking: either a maximum compression of the Brillouin solitons, or a stable splitting into N equally spaced pulses. Case N = 3 is more detailed. Experiment implies a slight polarization modulation by the phase modulation. Simulations carried out through the coherent three-wave model are in very good agreement for both mode-locking mechanisms. Introduction of a small amplitude modulation together with the intra-cavity phase modulation satisfactorily explains the stable splitting domain as well as the compression domain. published in Optics Common. 257 311-318 (2006) ∗correspondig author [email protected] 1 ha l-0 04 60 39 2, v er si on 1 28 F eb 2 01 0 Author manuscript, published in "Optics Communications 257 (2006) 311–318" DOI : 10.1016/j.optcom.2005.07.049