2.8-µm polarization-maintaining Er fiber laser mode-locked by a GaSb-based SESAM.

A GaSb-based SEmiconductor Saturable Absorber Mirror (SESAM) enables continuous-wave picosecond mode-locked operation with excellent stability of a polarization-maintaining mid-infrared Er:ZBLAN fiber laser. The GaSb-based SESAM mode-locked fiber laser delivers an average output power of 190 mW at 2.76 µm at a repetition rate of 32.07 MHz (corresponding to a pulse energy of ∼6 nJ) and exhibits a high signal-to-noise ratio of ∼80 dB. The polarization extinction ratio is more than 23 dB. By employing an intracavity diffraction grating, the laser wavelength is continuously tunable across 2.706-2.816 µm. Passively Q-switched operation of this laser is also demonstrated.

Deep-red double-clad fiber laser at 717†nm.

We report on a double-clad fiber laser operating on the 3P0 → 3F4 Pr3+ transition (in the deep-red spectral range) pumped by a GaN diode laser at ∼442 nm. It employs a 0.8-mol% PrF3-doped ZBLAN double-clad fiber with a 7.5-µm core, a double D-shaped inner cladding, and a length of 3.0 m. The laser delivers a maximum output power of 0.71 W at 716.7 nm with a slope efficiency of 9.0% (versus the launched pump power) and a laser threshold of 0.90 W. The laser emission is partially polarized. The laser performance is simulated providing a guideline for watt-level deep-red fiber laser sources.

Watt-level visible laser in double-clad Pr3+-doped fluoride fiber pumped by a GaN diode.

We report on a red praseodymium fiber laser delivering 1.07 W at 634.5 nm with a slope efficiency of 20.7% (versus the incident pump), a laser threshold of 0.55 W, and a single-mode output (Mx,y2<1.1) in the quasi-continuous-wave regime. It is based on a 0.6 mol.% Pr3+-doped ZBLAN double-clad fiber with a 5.5 µm core, a double D-shaped (diameters, 115/125 µm) inner cladding, and a length of 5.0 m. The fiber is pumped by a multimode 443 nm GaN diode. The laser design is optimized using a numerical model. The proposed concept is suitable for the development of diode-pumped high brightness watt-level visible praseodymium fiber lasers.

Directly diode-pumped mid-infrared dysprosium fiber laser.

We report the demonstration of a Dy3+-doped ZBLAN fiber laser directly diode-pumped at 800 nm utilizing a codoping scheme with Tm3+ serving as the donor ion. In this initial demonstration, a modest output power of 12 mW is generated with a slope efficiency of 0.3% at an emission wavelength of 3.23 µm. Energy transfer dynamics are investigated through excited state lifetime analysis and comparison to resonant pumping of the Dy3+ upper state. The likely presence of an energy transfer upconversion process is identified, which has an undesirable effect on 3 µm class lasers but may be of significant benefit for future 4 µm systems.