Exploring the spatial hole burning effect on the mode-locking characteristics of self-mode-locked Nd:YVO4 lasers

Abstract

The spatial hole burning (SHB) effect on the mode-locking characteristics of Nd:YVO4 self-mode-locked (SML) lasers are investigated. By varying the cavity length, pump power, and crystal temperature, we manipulate the SHB effect on the longitudinal mode distributions and the temporal waveforms of the SML lasers. The experimental results indicate that, at a pump power of 3395 mW and a cavity length of 23 mm, the SHB effect is minimal, the temporal waveform remains stable and the longitudinal mode spacing equals the fundamental longitudinal mode interval (FLMI). As increasing the cavity length to 75 mm, the experimental longitudinal mode spacing becomes 1 to 5 times the FLMI and the temporal waveforms are then multi-pulse mode-locked state, indicating an aggravation in the SHB effect of the SML laser. With the cavity length of 23 mm, as the pump power increases from 3.4 W to 9.7 W, the SHB effect on the mode-locking characteristics gradually also aggravates. The laser gradually changes from the fundamental mode-locked state to the spaced mode-locked state. By adjusting the crystal temperature from 25 °C to 35 °C, the aggravated SHB effect caused by the increase in pump power is counteracted.