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In this paper, we study the oxidation process during the heating of a titanium metallic surface by a Nd-YAG fiber pulsed laser beam under air environment. For this, we adopted an approach that considers a three-dimensional heat diffusion model coupled with an oxidation parabolic law (oxidation kinetics). The heat diffusion equation solved numerically, gives the temperature field. The oxide film growth is simulated by implementing a dynamic mesh technique. We developed computational procedures UDFs (User Defined Function) running interactively with the Fluent fluid dynamics software [ that implements the finite volume method. These UDFs are developed to insert the oxidation law, the temperature field, the specific boundary conditions and the mesh deformation into the calculation.

In this paper, we report a numerical study of a Nd:YAG solar laser side-pumped by a ring-array concentrator (RAC) system. We used the ZEMAX© and LASCAD© software to optimize a 1.5-m diameter RAC system, a 3V-shaped pump cavity within which a Nd:YAG single-crystal laser rod (4-mm diameter, 30-mm length) is mounted, and the laser resonator parameters. The multimode solar laser output power was numerically calculated to be 34.8 W in a continuous-wave mode, corresponding to a solar laser collection efficiency of 19.69 W/m2, a slope efficiency of 3.07%, and 2.3% solar-to-laser conversion efficiency, indicating an improvement of 2.05, 1.31, and 1.5 times, respectively, relative to that of the previous results for a side-pumped Nd:YAG solar laser. Moreover, this study is the first numerical analysis of a Nd:YAG solar laser side-pumped by a RAC concentrator.

A four-rod/four-TEM 00 -mode beam off-axis parabolic mirror solar pumping concept is proposed. Four off-axis parabolic mirrors with 10 m 2 total collection area were used as the primary solar concentrators to pump four 3.1-mm diameter, 84-mm length neodymium-doped yttrium aluminum garnet (Nd:YAG) rods within four 2V-shaped pump cavities through four secondary fused-silica aspheric concentrators and four rectangular fused-silica light guides, ensuring a good absorbed pump power distribution within each rod and avoiding the serious thermal lensing and thermal stress issues associated with classical single large rod solar lasers. The laser design parameters were optimized using ZEMAX © and LASer Cavity Analysis and Design (LASCAD © ) analysis software to maximize the TEM 00 -mode laser power. 155.29-W TEM 00 -mode total laser power was numerically calculated, corresponding to 15.5 W∕m 2 solar laser collection efficiency and 1.72% solar-to-TEM 00 -mode laser conversion efficiency, respectively. This result represents an improvement of nearly 2 and 1.24 times, in solar laser collection efficiency and solar-to-TEM 00 -mode laser conversion efficiency, respectively, as compared with the previous experimental records of the TEM 00 -mode solar laser pumped through the parabolic mirror primary concentrator. It provides also a 1.14 and 1.19 times improvement, as compared to the previous numerical record of the TEM 00 -mode solar laser pumped by the Fresnel lens primary solar concentrator.