In my view, the idea that optical PoW will reduce the energy cost of PoW mining is only temporary, because the Capex aspect of photonic miners is likely to be only a temporary competitive advantage - just like the Capex advantage of building ASIC miners is only a temporary, until each newer and more efficient ASIC is rolled out.

Photonic technology is new and not as readily available - for now.

If it turns out to be a way of minting money, demand will rise, and the competitive process of PoW will surely result in every photonic-miner owner trying to build a bigger, faster farm, just like all the others, and then we're right back to energy.