Generation of a train of ps-pulses from a diode pumped Nd-laser using electro-optical negative feedback

Mode locking with frequency dependent nonlinear mirror of Nd:YAG laser with electro-optical negative feedback has been presented. We use a LBO based nonlinear mirror thermally stabilized at a temperature corresponding to noncritical phase matching of the frequency doubling at 1.064 μm. Employing a resonator polarization output detected by a fast photodiode we control resonator losses through a Pockels cell. By creating a negative feedback we achieved q-switch suppression, thus stabilizing the mode-locking regime. Through a simple theoretical model we derived a relation for the laser parameters for stable laser operation. We achieved a stable train of picosecond pulses grouped in the 200 microsecond pump macropulse. Macropulse output energy is 4 mJ at a pump repetition rate of 400 Hz. The picosecond pulse train frequency determined by the resonator length is 115 MHz.