Efficient TEM00-mode solar laser using four Nd:YAG rods/four off-axis parabolic mirrors pumping approach

Abstract. A four-rod/four-TEM00-mode beam off-axis parabolic mirror solar pumping concept is proposed. Four off-axis parabolic mirrors with 10  m2 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 TEM00-mode laser power. 155.29-W TEM00-mode total laser power was numerically calculated, corresponding to 15.5  W  /  m2 solar laser collection efficiency and 1.72% solar-to-TEM00-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-TEM00-mode laser conversion efficiency, respectively, as compared with the previous experimental records of the TEM00-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 TEM00-mode solar laser pumped by the Fresnel lens primary solar concentrator.