Q-Switching and Mode-Locking of a 2.7 m Fluorozirconate Fiber Laser

Passive mode-locked and Q-switched operation of a 2.7 fluorozirconate fiber laser is reported. Q-switched pulses containing mode-locked pulse trains were generated by passive modulation with InAs layers used as saturable absorbers. The measured mode-locked pulse durations amounted to 2 ns, which was the resolution limit of the detection setup. Average output powers up to 16 mW could be obtained. 3 m lasers have many potential applications especially in the medical field due to the strong absorption of water in this range. Fiber lasers at this wavelength combine long interaction lengths and high power densities in the active core with negligible thermal problems, thus leading to potentially low thresholds and high efficiencies. The standard fiber laser in this range is the the Er3 –doped fluoride fiber laser at 2.7 m based on the IR glass ZBLAN utilizing the transition 4I11 2 4I13 2. This laser has been realized with threshold powers below 1 mW, with slope efficiencies exceeding 20 % and has also been laser diode pumped [1]. Many applications need high peak powers in short pulses, e.g. to reach power levels required for tissue ablation. This can be attained by Q-switching or mode-locking the laser. In the 3 m region, both techniques have been realized with crystal lasers both actively and passively [2, 3, 4]. Q-switching of a 2.7 m fiber laser utilizing an acousto-optic modulator was reported recently [5]. Mode-locking o