A. Brenier

Diode-pumped Yb:GGG laser: comparison with Yb:YAG

Abstract A diode-pumped ytterbium-doped Gd 3 Ga 5 O 12 (Yb:GGG) laser is reported for the first time. We report up to 4.2 W of CW laser power when pumping on the 971 nm absorption band with a 14 W fiber-coupled diode. The easy growth and the high thermal conductivity of Yb:GGG make it a challenger of Yb:YAG for high power applications. The efficiencies of these two crystals have been compared under the same pumping conditions, and turn out to be comparable.

Overview of the best Yb3+-doped laser crystals

Abstract Using a model for the quasi-three level laser dealing with gaussian waves, taking into account the saturation of the pump, the stimulated emission at the pump wavelength, the variation of the pump and laser waists along propagation (important for laser diode pumping) and the variation of the laser intensity along propagation, we evaluate the more promising Yb 3+ -doped crystals for laser applications: YAG, LNB, GdCOB, YCOB, YAB, C-FAP, S-FAP, KGdW, KYW, Sc 2 O 3 , Y 2 O 3 , Lu 2 O 3 . Our evaluation differs from Deloach et al. (IEEE J. Quant. Electron. 1993;29:1179). KYW, KGdW, YAB and Sc 2 O 3 are found to be the most efficient when considering the laser extracted power and the slope efficiency.

A new evaluation of Yb3+-doped crystals for laser applications

Abstract We develop a new model for the quasi-three-level laser. It deals with Gaussian waves, takes into account the saturation of the pump, the stimulated emission at the pump wavelength, the variation of the pump and laser waists along propagation (important for laser diode pumping) and the variation of the laser intensity along propagation. The model is used to evaluate the most promising Yb 3+ -doped crystals: YAG, GdCOB, YCOB, YAB, C-FAP, S-FAP, KGdW, KYW, for CW longitudinally pumped lasers. Our evaluation differs from Deloach and coworkers, devoted to Q -switched oscillators or nanosecond-pulse amplifiers. KYW, KGdW, YAB and GdCOB are found to be the most efficient when the laser extracted power and the slope efficiency are considered.

Growth, spectroscopic, and laser properties of Yb 3+ -doped Lu 3 Al 5 O 12 garnet crystal

We have grown high-quality LuAG:Yb3+ crystals with 0.75, 3.8, 10, 12, 15, 20, and 50 at. % concentrations by the vertical Bridgman method. With low-temperature spectroscopy the Stark sublevel structure of the 2F7/2 ground state and the 2F5/2 excited state has been determined. With room-temperature spectroscopy, the emission cross section was found to be 3×10−20 cm2, being 1.5 times the YAG:Yb3+ emission cross section. The luminescence quantum efficiency was measured in samples with different Yb3+ concentrations. Its value was found to be 90% for 3.8 and 10 at. %, 84% for 20 at. %, and 70% for 50 at. % Yb3+. The laser-emission tunability under diode pumping was found to extend from 1045 up to 1095 nm in a 12 at. % sample with 3.15 mm thickness.

The self-doubling and summing lasers: overview and modeling

We present an overview of the self-frequency doubling and summing lasers and we give the main optical and spectroscopic properties of the materials used in these devices. We describe a new self-doubling laser model (four and quasi-three level lasers) leading to a comparison of the different crystals (Nd-doped LNB, YAB, BNN, GdCOB and Yb-doped LNB, YAB, GdCOB) and to useful predictions on the choice of important parameters as the dopant concentration and the crystal length.

Spectroscopic properties of Pr3+-doped Ca4GdO(BO3)3 (GdCOB)

The main spectroscopic properties (absorption, emission, decay times) of Pr3+-doped Ca4GdO(BO3)3 (GdCOB) have been determined for the three X, Y, Z polarizations. The Judd–Ofelt analysis, extended to anisotropic crystals, normalized and modified to take into account the influence of the 4f5d lowest energy level, has been performed and gives reasonable agreement with experimental data. The band energy approach is used for estimations of probabilities of relative cross relaxations and multiphonon relaxation.

Evaluation of Nd3+-doped BiB3O6 (BIBO) as a new potential self-frequency conversion laser crystal

Abstract We present at room temperature emission and absorption spectra of new-synthesised Nd 3+ -doped BiB 3 O 6 (BIBO) in X -, Y -, Z -polarisations. The measured Nd 3+ concentration in the crystal remains low (1.08×10 19 ions/cm 3 ) and prevents up to now laser oscillation. The Judd–Ofelt analysis was performed with the results: Ω 2X =0 cm 2 , Ω 4X =0.556×10 −20 cm 2 , Ω 6X =0.227×10 −20 cm 2 , Ω 2Y =0 cm 2 , Ω 4Y =0.307×10 −20 cm 2 , Ω 6Y =0.177×10 −20 cm 2 , Ω 2Z =0.069×10 −20 cm 2 , Ω 4Z =0.433×10 −20 cm 2 , Ω 6Z =0.117×10 −20 cm 2 . The highest emission cross-section near 1079 nm is 2.2×10 −20 cm 2 . The 4 F 3/2 emission lifetime is 53 μs . Low temperature spectroscopy reveals that there is only one kind on Nd 3+ emitting centre which substitutes Bi 3+ cations. We evaluate the ability of the material to be a self-frequency conversion laser crystal by calculating the phase matching directions, the effective nonlinear optical coefficients and the effective emission cross-sections for self-frequency doubling, self-sum and difference frequency mixing. We have found that the emission peak at 1069 nm existing mainly for Y -polarisation was the most favourable with directions of propagations in the YZ -plane ( φ =90°) for self-sum frequency mixing and in the XZ -plane ( φ =0°) for the self-difference frequency mixing. For these directions the effective nonlinear optical coefficient (up to 3.2 pm/V) and the effective emission cross-section have simultaneously the highest values.

Structural and Spectroscopic Characterization of Nominal Yb3+:Ca8La2(PO4)6O2 Oxyapatite Single Crystal Fibers Grown by the Micro-Pulling-Down Method

Yb-doped Ca8La2(PO4)6O2 (CLPA) single crystals with the apatite-type structure and having orientation were grown by the micro-pulling-down (μ-PD) method. The apatite structure is represented by the monophased field of Ca8(La2–xYbx)-(PO4)6O2 (CLYPA) where it is assumed that 2 Ca2+ sites are substituted by La3+ and Yb3+ cations. Its monophased range was found to be from x = 0.0 to 0.2. The segregation of Yb3+ in CLPA single crystals and the maximum Yb3+ concentration are discussed. The crystallinity was studied using X-ray rocking curve analysis. Absorption, emission and fluorescence decay studies of Yb3+ ions in CLPA were also carried out both at low temperature and room temperature. Spectroscopic data reveal Yb3+ ion occupation within different crystallographic sites of the apatite-type structure. The potential for a diode-pumped Yb3+ laser is evaluated.

Laser heated pedestal growth and optical properties of Yb3+-doped LiNbO3 single crystal fibers

Abstract The elaboration of Yb3+-doped LiNbO3:Sc3+ and LiNbO3:Mg2+ single crystal fibers by the laser heated pedestal growth technique is reported. The ytterbium emission and absorption cross-sections are given. We show that it is possible to obtain the coincidence between the wavelength of phase-matching for second harmonic generation and the wavelength of laser emission by varying the host composition, in order to achieve a self-doubling laser material.

Influence of high pressure on the luminescence transitions of Mn4+-doped gadolinium gallium garnet

We present results of a high-pressure photoluminescence study of Mn- and Ca-doped gadolinium gallium garnet (GGG) crystals. Since the Mn4+ ion has the same electronic structure of the open 3d3 shell as Cr3+, its spectroscopic properties are expected to be similar to those of the Cr-doped GGG. We observed the luminescence R-lines of various Mn4+ centres in GGG. In the 0–118 kbar pressure range those R-lines shift linearly to lower energies. The pressure coefficients are of the order of 2 cm−1 kbar−1, about three times larger than that for Cr3+ ions. This fact can be explained by different strength of coupling of isoelectronic Cr3+ and Mn4+ ions with GGG host. The changes of the radiative decay times of the Mn4+ centres as a function of pressure are fitted with a theoretical model.