We report on a very highly doped and very highly efficient cladding pumped single mode Tm3+ silica fiber laser operating at 1.985 microns. The preform was fabricated using a proprietary all halide vapor phase modification of the MCVD process. The preform core has a maximum Tm2O3 doping concentration of greater than 8.5 wt%. A laser based on the resulting double clad fiber was pumped at 793 nm and demonstrated a record slope efficiency of 74.5 % wrt absorbed pump power.
We report the fabrication of extremely low NA preforms (<0.03), highly doped with Yb using a conventional Modified Chemical Vapor Deposition (MCVD) system. Our lowest NA preform (0.025 NA) was drawn to a 52um core step-index double-clad fiber operating in a single mode regime (M<sup>2</sup>=1.04). The fiber had a mode field diameter (MFD) and an effective area (A<sub>eff</sub>) greater than 35um and 1000um<sup>2</sup> respectively. In a fiber laser configuration, the efficiency was greater than 85% without any sign of photodarkening. To the best of our knowledge, by using our extremely low NA preforms we have demonstrated the largest MFD and A<sub>eff</sub> to date for a single-mode step index double–clad Yb doped fiber without involving any micro-structuration.
We present a 3kW single-mode fiber laser based on an Yb-doped LMA fiber operating at 1080nm. The laser which is pumped by 9xxnm diode bars stacks. It is believed to be the highest power direct diode pumped single-mode fiber laser oscillator to date.
This communication describes the fabrication of Yb doped silica preforms by modified chemical vapor deposition
(MCVD) method using Yb(C<sub>11</sub>H<sub>19</sub>O<sub>2</sub>)<sub>3</sub> and AlCl<sub>3</sub> in vapor phase. In order to investigate the optical quality of the
preforms a systematic spectroscopic study was carefully carried out on various samples with different Yb and Al doping
levels. In this way, the influence of the preforms composition on the Yb spectroscopic properties was studied in details,
allowing the prediction of the composition favoring the laser emission with the highest efficiency. The predictions have
then been validated after pulling the preforms in large mode area fibers (LMA).
We present here the first CW high power laser operation obtained under diode-pumping with an Yb<sup>3+</sup>:CaF<sub>2</sub> crystal. This crystal exhibits good thermo-optical properties and can easily be grown in bulk crystals or in thin films. A maximum power of 5.8 W in a diffraction limited beam has been obtained with a 5% ytterbium-doped crystal of 4 mm-long. Moreover, the laser wavelength has been tuned over 54 nm, between 1018 and 1072 nm, and the double-pass small-signal gain has been measured to be more than 1.8, showing the great potential of Yb<sup>3+</sup>:CaF<sub>2</sub> as a gain media for ultra-short pulses operation or as amplifier.
By using laser selective excitation and low temperature time-resolved spectroscopy techniques, we have been able to experimentally identified the ion centers of tetragonal, trigonal and cubic symmetries in a low concentrated crystal as 0.03%Yb<sup>3+</sup>:CaF<sub>2</sub>. This low temperature study was then completed by an analysis of the room temperature spectroscopic properties and of the laser potential of more concentrated Yb<sup>3+</sup> doped CaF<sub>2</sub> single crystals grown in our laboratory. A laser slope efficiency of 50% with respect to the absorbed 920 nm pump power was obtained, and the laser wavelength could be tuned between 1000 to 1060 nm.