Harmonic mode locking underneath the Q-switched envelope in passively Q-switched mode-locked Nd:GdTaO₄ 1066 nm laser

In this work, harmonic mode locking in a laser diode pumped passively Q-switched mode-locked Nd:GdTaO₄ 1066 nm laser is presented by using Cr⁴⁺:YAG as saturable absorber. The average output power of the passively Q-switched mode-locked 1066 nm laser reaches 4.7 W with a repetition rate of 200.0 MHz and a pulse width of ~1.3 ns within a Q-switched envelope of 150.0 ns. By changing the Z-type cavity length, high-order harmonic mode locking operation of the passively Q-switched 1066 nm laser is conducted. The 3rd-order harmonically mode-locked 1066 nm laser yields a maximum average output power of 3.2 W and a pulse width of ~570 ps at 164.5 MHz repetition rate inside a Q-switched envelope of 419.7 ns long. The pulse repetition rate reaches 655.3 MHz in the 9th-order harmonically mode-locked 1066 nm laser.