Even if semiconductor lasers could put out the power required (they can't...), a 20x improvement would still mean the efficiency is only around 20%, so you'd st

Even if semiconductor lasers could put out the power required (they can't...), a 20x improvement would still mean the efficiency is only around 20%, so you'd still be putting in 10 MJ to get out 2 MJ... Yes, it's better, but the argument still holds