A high average power and high beam quality picosecond laser system combined with diode-end-pumped Nd:YVO4 and laser diode-side-pumped Nd:YAG amplifier is described. The system combines the advantages of Nd:YVO4 crystal having large stimulated-emission cross section and Nd:YAG crystal having good thermal conductivity. The diode-end-pumped Nd:YVO4 amplifier allows the laser from the oscillator to obtain high gain so that the laser can amplify rapidly and the diode-side-pumped Nd:YAG amplifier benefits to obtain high output power. The Nd:YAG amplifier is designed as double-pass form to increase t...