Numerical simulation of subnanosecond single mode-locking pulse generation in a doubly Q-switched and mode-locked green laser with EO and Cr^4+:YAG

Abstract

Under the Gaussian spatial distribution approximation, the coupled rate equations for a diode-pumped, dual-loss-modulated, Q-switched, and mode-locked (QML) green laser with EO and Cr4+:YAG are derived. The numerical simulation results show that the pulse width of the Q-switched envelope is related to the pump power, repetition rate of EO, initial transmission of Cr4+:YAG, and the stimulated emission section of the gain medium. By designing the related parameters well, the pulse width of the Q-switched envelope can be greatly compressed to shorter than the cavity roundtrip transmit time, i.e., the interval of two neighboring mode-locking pulses; then subnanosecond single mode-locking pulses with low repetition rate, high pulse energy, and high stability can be obtained. The generation conditions of subnanosecond single mode-locking pulses per envelope in a dual-loss-modulated QML Nd:Lu0.15Y0.85VO4 green laser with EO and Cr4+:YAG are experimentally demonstrated and found to be in agreement with the theoretical results.