Alberto Sottile

Influence of other rare earth ions on the optical refrigeration efficiency in Yb:YLF crystals

We investigated the effect of rare earth impurities on the cooling efficiency of Yb³⁺:LiYF₄ (Yb:YLF). The refrigeration performance of two single crystals, doped with 5%-at. Yb and with identical history but with different amount of contaminations, have been compared by measuring the cooling efficiency curves. Spectroscopic and elemental analyses of the samples have been carried out to identify the contaminants, to quantify their concentrations and to understand their effect on the cooling efficiencies. A model of energy transfer processes between Yb and other rare earth ions is suggested, identifying Erbium and Holmium as elements that produce a detrimental effect on the cooling performance.

Multiple polarization orange and red laser emissions with Pr:BaY 2 F 8

We investigated the polarization of continuous-wave laser emission in the orange region, at 607 nm, and in the red region, at 639 nm and 643 nm, from a Pr:BaY2F8 (Pr:BYF) crystal, pumped by a 445 nm laser diode. We achieved linearly polarized emission along two optic axes of the crystal by changing its orientation with respect to the pump. Simultaneous emission of two orthogonal linear polarizations was observed in the orange region, at the same wavelength, and in the red region, with concurrent emission from the two separate lines.

Deep red diode-pumped Pr 3+ :KY 3 F 10 continuous-wave laser

We report the first observation of continuous-wave laser emission at 720 nm, in the deep red region, of a Pr3+:KY3F10 (Pr:KYF) single crystal, pumped with a blue InGaN-based laser diode at 446 nm. We employed a hemispherical cavity with three different output coupling mirrors transmitting 0.7%, 1.4%, and 2.7% of laser radiation. We obtained a maximum output power of 207 mW with a slope efficiency of 24.3%, comparable for the first time to what has been reported for other praseodymium-doped fluoride crystals. The round-trip cavity losses for our sample were estimated to be between 0.3% and 0.6%, a remarkably small value for this material.

Visible laser operation in a Pr 3+ :LiLuF 4 monocrystalline fiber grown by the micro-pulling-down method

We report on the growth and laser operation of a fiber-shaped single crystal of Pr3+:LiLuF4 (Pr:LLF) grown by the micro-pulling-down (µ-PD) method. We checked the optical quality of the crystal by measuring its spectroscopic features, and by observing the profile of a laser beam transmitted through it. Using an InGaN laser diode as pump source, we achieved continuous-wave laser emission in the orange, red, and deep red regions, with slope efficiencies comparable with or exceeding previous reports on this material. To the best of our knowledge, this work represents the first observation of visible laser emissions from a crystal grown by the µ-PD technique.

Effect of impurities on cooling efficiency in fluoride crystals

We present a characterization of the optical refrigeration properties of two 5% Ytterbium-doped YLF crystals. Measurements showed different cooling efficiencies for the samples, despite the same concentration of dopant. We carried out a spectroscopic study on the crystals devoted to the identification of foreign contaminants inside them. These searches determined the presence of Erbium and Holmium impurities in both the cooling samples. We attributed the reduction of the cooling efficiency in one of the crystals to an increased amount of these contaminants.

Wavelength tuning in a diode-pumped Pr 3+ :Ba(Y 0.8 Lu 0.2 ) 2 F 8 laser

Research on praseodymium-doped solid-state lasers is seeing a renovated interest in the last years. Among the best crystal hosts for these lasers, BaY2F8 (BYF) shows some peculiarities, such as its monoclinic structure and its wide Stark splitting, which allow enhanced power scalability and broad tunability. However, BYF is considered troublesome to grow, and sometimes can crack during handling. To prevent these issues, Ba(Y1−xLux)2F8 (BYLF) has been proposed as a new host material [1]. BYLF is isomorphic to BYF, keeping all the advantages of its structure. Thanks to the addition of lutetium, BYLF should have better thermo-mechanical properties and overall it has shown laser performances than BYF [2].

Ultrafast Laser Inscribed Pr:KY 3 F 10 Waveguides for Dual Wavelength and Switchable Waveguide Lasers in the Visible

Diode pumped fs-laser written Pr:KY3F10 waveguide lasers with 42 mW output power in the visible spectral region are presented. Utilizing polarization dependent spectroscopic properties of cubic Pr:KY3F10 dual wavelength and switchable laser operation was achieved.