1.34 μm Nd:YVO4 laser mode-locked by a single-walled carbon nanotube saturable absorber

Abstract

Passive mode-locking of 1.3 μm solid-state lasers is problematic for semiconductor saturable absorber mirrors (SESAMs) not only because of difficulties in their fabrication process but also in relation to the achievable parameters and damage resistivity. In contrast, single-walled carbon nanotube saturable absorbers (SWCNT-SAs) exhibit broadband absorption which is controllable by varying the nanotube diameter and chirality, and require relatively simple manufacturing processes. Here we report on steady-state mode-locked operation of a diode pumped Nd:YVO 4 laser on the 4 F 3/2 → 4 I 13/2 transition at 1.342 μm using a transmitting SWCNT-SA. The SWCNT-SA employed in the present work was fabricated by SWCNTs grown by high-pressure CO conversion technique, showing broad absorption around 1.3 μm. The linear transmission at the laser wavelength was about 99%. The Nd:YVO 4 laser was longitudinally pumped by the unpolarized radiation of a 808 nm fiber-coupled laser diode. The ~1.2-m long cavity was optimized for large fundamental mode size. Above threshold the laser operated first in the CW mode, then had a range of Q-switched modelocked operation before reaching the regime of stable steady-state mode-locking. With an output coupler of 90% reflectivity, the average output power in the steady-state mode-locked regime reached 0.8 W at a slope efficiency of 14.5% with respect to the incident pump power. At a repetition rate of 127 MHz this corresponds to single pulse energy of 6.3 nJ. Such pulse energies are comparable to the best results obtained using SESAMs but the pulse duration of 16.5 ps measured in the present experiment is substantially shorter.