Optical restrictions on the design of a solar pumped laser are related to the collection of the sunlight and the required opto-mechanical assembly to provide end pumping of a small Nd:YAG laser rod. Solar pumping influences affect the laser operation. Simultaneous mode-locking and frequency-doubling are additional complications.
J. D. Barry,
C. J. Kennedy,
"Frequency Doubling Of A Solar Pumped Nd:YAG Laser", Proc. SPIE 0122, Advances in Laser Engineering I, (20 October 1977); doi: 10.1117/12.955784; https://doi.org/10.1117/12.955784