Dual-rod pumping approach for tracking error compensation in solar-pumped lasers

We present here a tracking error compensation concept in solar-pumped lasers, by pumping two thin laser rods simultaneously, each rod by half of the solar collector area instead of the mostly used scheme with one thick rod pumped by a full solar collector area. A semicylindrical fused silica lens allows an efficient focusing of the concentrated solar power from the focal spot of the parabolic mirror into the two thin laser rods mounted within two compound parabolic concentrator-semicylindrical pump cavities. The multimode solar laser output power, the threshold pump power, and the slope efficiency of a single-rod scheme, a dual-rod scheme with two laser beams, and a dual-rod scheme with one laser beam are calculated both numerically and analytically, revealing a clear advantage of the dual-rod one laser beam scheme in terms of solar laser output power and threshold pump power. A large improvement in tracking error compensation capacity is numerically attained with this new approach, leading to 2.57 and 3.00 times enhancement in tracking error width at 10% laser power loss in δY (altitude) and δX (azimuth) errors, respectively, as compared to the most efficient end-side-pumped scheme by the same collection area.