Stable mode-locked operation of a low repetition rate diode-pumped Nd:GdVO4 laser by combining quadratic polarisation switching and a semiconductor saturable absorber mirror

In this paper, we present the mode-locked operation of an ultra-robustly stabilised Nd:GdVO4 laser with low repetition rate by combining quadratic polarisation switching and a semiconductor saturable absorber mirror (SESAM). In addition, similar experiment was also done with Nd:YVO4. For Nd:GdVO4, 16-ps pulses at 1063nm with a repetition rate of 3.95MHz have been obtained for a laser average output power of 1.4W. For Nd:YVO4, the performance was 2.5W of average power for 15-ps pulses at 1064nm. Moreover, we demonstrate experimentally the advantage of combining these two passive mode locking techniques in terms of stability ranges. We show how the dual mode-locking technique is crucial to obtain a stable and long-term mode-locked regime in our case of a diode-pumped Nd:GdVO4 laser operating at low repetition rate and more generally how this dual mode-locking technique improves the stability range of the mode-locked operation giving more flexibility on different parameters. (c) 2006 Optical Society of America