Matteo Vannini

High-efficiency, high-power and low threshold Yb 3+ :YAG ceramic laser

We present a high-power, high-efficiency and low threshold laser prototype based on doped ceramic Yb(3+):YAG. We achieved an output power of 9 W with a slope efficiency of 73% and a threshold of 1 W at 1030 nm in quasi-Continuous Wave (QCW). Moreover, we obtained an output power 7.7 W with a slope efficiency of 60% in Continuous Wave (CW). Finally, a characterization of a low losses tunable cavity for several laser wavelengths with an output power exceeding 5 W is reported.

Effects of the excitation density on the laser output of two differently doped Yb:YAG ceramics

We report the behavior of two Yb(3+) doped ceramics (i.e. 10% at. and 20% at.) under quasi-continuous wave laser pumping. Two different behaviors are found depending on the density of Yb(3+) in the excited level. Experimental results show that at low population inversion density, the maximum output power and the efficiency are almost independent on the doping concentration. In particular, an output power as high as 8.9 W with a corresponding slope efficiency of 52% with respect to the injected pump power was reached with the 20% at. sample. Conversely, at high population inversion densities, the 20% doped sample shows a sudden decrease of the laser output for increasing pump power, due to the onset of a nonlinear loss mechanism. Finally, we report a comparison of the experimental results with numerical simulations for the evaluation of the inversion density and of the temperature distribution.

High efficiency room temperature laser emission in heavily doped Yb:YLF.

We report the tunable, CW and quasi CW laser operation at room temperature of an highly doped (30% at.) Yb:YLF crystal longitudinally pumped by a fiber coupled laser diode array. The CW output power is 1.15 W vs. an absorbed pump power of 6 W, with a slope efficiency of 31%. In quasi-CW operation (20% duty factor @10 Hz) an output power of 4 W with an absorbed power of 9.5 W, and a slope efficiency of 62.8% were obtained. The tuning range spans from 1022 to 1075 nm. To our knowledge, these are among the best experimental results obtained at room temperature with Yb doped YLF.

3-D numerical simulation of Yb:YAG active slabs with longitudinal doping gradient for thermal load effects assessment.

We present a study of Yb:YAG active media slabs, based on a ceramic layered structure with different doping levels. We developed a procedure allowing 3D numerical analysis of the slab optical properties as a consequence of the thermal load induced by the pump process. The simulations are compared with a set of experimental results in order to validate the procedure. These structured ceramics appear promising in appropriate geometrical configurations, and thus are intended to be applied in the construction of High Energy Diode Pumped Solid State Laser (DPSSL) systems working in high repetition-rate pulsed regimes.

CW and quasi-CW laser performance of 10 at.% Yb3+:LuAG ceramic

We have investigated the laser oscillation of 10xa0at.% Yb3+:LuAG ceramic pumping into the two main absorption peaks in CW and quasi-CW operation modes. Emitting at 1030 and 1046xa0nm the laser achieves excellent performance, delivering output powers up to 8.8xa0W. The highest estimated slope efficiencies are 72.6% in CW and 79% in quasi-CW. A tunability range of 57.5xa0nm is measured.

First laser oscillation and broad tunability of 1 at. % Yb-doped Sc 2 O 3 and Lu 2 O 3 ceramics

We report the first oscillation achieved on 1u2009at. % Yb-doped Sc2O3 and Lu2O3 ceramics under quasi-CW pumping at 968u2009nm. With Sc2O3 we measured a maximum output power of 2.2u2009W with a slope efficiency of 59% at 1040.5u2009nm. Comparable results are obtained with Lu2O3 at 1032.5u2009nm, i.e., 1.8u2009W with a corresponding slope of 45%, while at 1078u2009nm we measured 1.5u2009W with 34% of slope efficiency. Finally, we present the range of tunability, which exceeds 41u2009nm for both samples. To the best of our knowledge, these are the first measurements reported in literature either in terms of laser emission or continuous tunability range achieved with 1u2009at. % doping level.

A ceramic based Yb3+:YAG laser

We report the performance of a laser based on a 9.8% doped ceramic Yb3+:YAG operating in quasi-Continuous Wave (QCW) and in Continuous Wave (CW) at room temperature. The maximum output power of 9 W with a slope efficiency of 73% at 1030 nm was achieved in QCW. We investigated the problems originated from thermo-mechanical properties of the ceramic and we studied their effects on the laser per-formance finding that either the slope efficiency or the laser threshold are thermal-losses independent. Finally, we report a characterization of a low losses tunable cavity for several laser wavelengths.

Experimental evaluation of the cw lasing threshold for a Ce:LiCaAlF6 laser.

We present an experimental technique that allows the direct measurement of the continuous wave (cw) lasing threshold and the slope efficiency of a Ce:LiCaAlF6 (Ce:LiCAF) laser source by means of time-resolved measurement in the pulsed regime. We used a long-pulse-duration source to pump a tunable laser and a high-efficiency nondispersive laser in a quasi-stationary lasing regime. We compare the experimental results with earlier theoretical evaluations, and we demonstrate the feasibility of a cw Ce:LiCAF laser. Under the conditions discussed here, our technique can be applied to all the active media that achieved pulsed laser emission to investigate their potential as cw laser active media.

Characterization and comparison of 1% at Yb-doped Lu2O3 and Sc2O3 ceramics as laser gain media

We present the first laser oscillation achieved on Yb-doped Sc2O3 and Lu2O3 ceramics with a level of doping as low as 1 at %, under quasi-continuous wave pumping at 968 nm. Ceramic samples reached comparable performances in terms of tunability ranges, which exceeds 41 nm, and laser output powers. In particular, with the former sample emitting at 1040.5 nm we measured a maximum output power of 2.2 W with a corresponding slope efficiency of η = 59%. The latter medium delivered 1.8 W with a slope of η = 45% at 1032.5 nm while at 1078 nm we measured 1.5 W with η = 34%. Finally, we report the measured level of the Amplified Spontaneous Emission (ASE) for both samples, which was found to be less than 0.1 mW at the maximum pump power.

High efficiency laser action of 1% at. Yb 3+ :Sc 2 O 3 ceramic

We report the spectroscopic characteristics and the laser performances of a low-doped 1% at. Yb:Sc(2)O(3) ceramic sample. Under end- pumping at 933 nm and 968 nm in quasi-CW mode, at 1040.5 nm the laser delivers a maximum output power of 4.3 W and 1.77 W, respectively with a corresponding slope efficiency of 74% and 80%, which are, to the best of our knowledge, the highest value reported in literature for ceramics. We explored the tuning range of the sample, which spans from 1005 nm to 1050.5 nm, and finally we characterized the low losses tunable cavity at 1032 nm.