Cost-effective method for computational prediction of thermal conductivity in optical materials based on cubic oxides.

In this paper we report on a computationally cost-effective method designed to estimate the thermal conductivity of optical materials based on cubic oxide including mixed ones, i.e. solid solutions of different oxides. The proposed methodology take advantage from Density Functional Theory (DFT) calculations to extract essential structural parameters and elastic constants which represent the inputs for revised versions of Slack and Klemens equations relating thermal conductivity to elastic constants. Slack equation is modified by the introduction of a corrective factor that incorporates the Grüneisen parameter γ, while in the revised Klemens equation a distortion parameter d accounting for the impact of point defects on lattice symmetry is added, which is a critical factor in determining thermal conductivity in optical materials with mixed compositions. The theoretical results were found in good agreement with experimental data, showing the reliability of our proposed methodology.

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.

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.

Time-dependent analysis of a parametric lens detected with a 100-fs Ti:sapphire laser.

The second-order parametric lens effect shows a temporal limit as a saturable-absorber device for operation in the ultrafast time region. We present and discuss an extended theoretical model dealing with second-order cascaded processes in a nonstationary condition. Experimentally we report the detection of the time-averaged lens effect in the hundred-of-femtoseconds range, discussing the limits that arise in this ultrafast optical region.

Efficient second harmonic generation in beta-barium borate by a diffraction-limited copper vapor laser.

The diffraction-limited beam of a copper vapor laser employing a self-filtering unstable resonator was used to induce second harmonic generation in a nonlinear crystal of beta-barium borate. Despite the moderate emission characteristics of our small-scale laser device (1.5-W average power, 25-kW peak power at 511 nm), we obtained average and peak power conversion efficiencies of approximately 20 and 30%, respectively, which improved on the previously reported results by a factor of 2.