Abstract

Passive Q-switching based on cooperative dynamics of linear Rayleigh backscattering (RS) and Stimulated Brillouin Scattering (SBS) has been reported for fiber lasers with the geometry similar to shown in Fig. 1.¹⁻⁴ The matter of the mechanism is the following. At the beginning of every cycle, the population inversion in the fiber amplifier builds up and lasing in the fiber linear cavity (at frequency v_A) occurs due to reflection from the FBG and backreflection caused by RS in the fiber ring resonator. RS feedback provides a very effective linewidth narrowing of laser radiation creating the conditions for SBS. The growth of SBS inthe ring (at frequency V_B = V_A-Δv_SBS, where Δv_SBS is the SBS shift) then causes a series of avalanche processes leading to Q-switching. Passive Q- switching in rare-earth-doped fiber lasers has been observed experimentally with 2-3 W^1,2 and 30-80 mW^3,4 pump powers. At low pump power level, the laser dynamics is well described by the RS-SBS model. In this case the jitter of V_A, is found to be the main destabilizing factor for the laser performance. At high pump power, the RS-SBS process is complicated by multiplicity of competitive nonlinear effects (including generation of high-order SBS components), whose also lead to impairment of the laser stability.

© 2002 Optical Society of America