Q-switched laser combined with electric-optic modulator and GaAs saturable absorber

In order to study the symmetry of Q-switched laser pulse,combined with a electric-optic(EO) modulator and a GaAs saturable absorber,an active-passive Q-switched laser is realized.Especially,the more symmetric and shorter pulse is generated in comparison with only EO-active or GaAs-passive Q-switched laser.The compressed ratio is higher than 40%.In addition,a symmetric factor is defined to describe the temporal symmetry of the pulses and the improvement of the pulsed symmetry is higher than 10%.The coupled rate equations under the plane-wave approximation are used to simulate the Q-switched process of the laser,and the numerical solution accords well with the experimental results.