There is at least one tuneable laser (I’m not current, as it were, on lasers), but I don’t think laser efficiency is adequate for the task you suggest.
Yes, lasars are only about 1% efficient. The free electron lasar is in use in Idaho but again, you have to go for rare and expensive isotopes to make it worth the energy input. They also use it to remove radioactive isotopes(remediate nuclear waste)but LENR is far better at that. But there too many yucca mountain financial toes are stepped on and dingy harry(D-NV)wouldn’t lift a finger there to help, too much federal patronage involved.
The spectrum-spray from a synchrotron would be more viable : thru sapphire windows/fiber optics cables/to capacitor grids where individual species of isotopes are ionized/bond w/the substrate(in a large helium-flow pipe).
This polariton process supposedly produces lasar light more efficiently, could it be tuneable to operate the RIS process so as to turn garbage, even nuc-rad-waste, into pure isotopes? If so, land fills become gold mines....