A fiber laser system is configured with a nonlinear resonator cavity which includes a plurality of mirrors. One of the mirrors is a piezoelectric mirror capable of being displaced between multiple positions in response to a control signal generated by a digital controller. The generation of the control signal is caused by mismatch between a fundamental frequency, imputed into the resonant cavity and further split by a nonlinear crystal into resonant and harmonic frequencies, and the resonant frequency. The positions of the piezoelectric mirror and time interval the piezoelectric mirror may occupy these position are controlled so that the output radiation at the harmonic may be periodically interrupted which results in a pulsed output radiation.