While heating something that hot using “passive” components (is a laser really passive?) is awesome, is it really useful? 5500K is considerably hotter that, say, the combustion chamber of a rocket, and those chambers need active cooling. And even 1500K is plenty hot that the Carnot efficiency of the heat engine part will be high.
Also, a solar pumped laser needs cooling, just like a heat engine! Just from first principles, you can’t have a gadget at thermal equilibrium that magically produces an excess of light at its output frequency — this would violate the second law of thermodynamics.
And if you imagine a model three-level laser, exposing all three transitions to bright light will pump the nonlasing intermediate transition (overfilling level 2, thus reducing the population inversion in a laser lasing on the 3 -> 2 transition, or pumping useful level 2 atoms back up to level 3 in a laser lasing on 2 -> 1) and will actively un-pump the lasing transition in any variety of laser (because light in the wrong mode will cause a population-inverted transition to emit into that same wrong mode by simulated emission).
Also, a solar pumped laser needs cooling, just like a heat engine! Just from first principles, you can’t have a gadget at thermal equilibrium that magically produces an excess of light at its output frequency — this would violate the second law of thermodynamics.
And if you imagine a model three-level laser, exposing all three transitions to bright light will pump the nonlasing intermediate transition (overfilling level 2, thus reducing the population inversion in a laser lasing on the 3 -> 2 transition, or pumping useful level 2 atoms back up to level 3 in a laser lasing on 2 -> 1) and will actively un-pump the lasing transition in any variety of laser (because light in the wrong mode will cause a population-inverted transition to emit into that same wrong mode by simulated emission).