The classic book about this kind of approach is Goodman: https://www.amazon.com/Introduction-Fourier-Optics-Joseph-Go...
It's basically a hardware accelerator for a convolution - an important step in a neural network, but it isn't a general purpose processor (so beware their benchmarks of "Ops per second" - these aren't equivalent to CPU/GPU ops.)
I wonder if this might be the end of the silicon valley (in California) and the beginning of the photonic valley (in Texas).
(photonic valley? optical valley?)