The Multipeak Phenomena and Nonlinear Effects in ${Q}$ -Switched Fiber Lasers

We investigate control of the Q-switch rise time as a means to eliminate the undesirable formation of multipeak structure within actively Q-switched fiber lasers. Our experiments show that the development of pulse substructure is solely due to gain dynamic effects and that nonlinearity does not play a decisive role in the process. Using a spectrally resolved optical time gating technique, we investigate nonlinear pulse evolution for both smooth and structured Q-switch pulses of otherwise similar characteristics in Q-switch cavity comprising anomalously dispersive fiber. Useful insight is obtained into the complex interplay of the gain dynamic and various nonlinear effects governing the detailed pulse evolution. The measurements highlight the value and potential of this characterization technique for studying such lasers.