[qwezxcrty]

I think the most fundamental reason is that there is no efficient enough nonlinearity at optical frequencies. So two beams(or frequencies in some implementation) tends not to affect each other in common materials, unless you have a very strong source (>1 W) so the current demonstrations for all-optical switching are mostly using pulsed sources.

[perlgeek]

As somebody who tried to do a PHD in optical communications, this is 100% correct.

I wonder if meta material might provide such nonlinearities in the future.

[ls612]

I wonder if considerably more engineering and research effort will be applied here when we reach the limit of what silicon and electrons can do.

[cycomanic]

No this is not an engineering issue, it's a problem of fundamental physics. Photons don't interact easily. That doesn't mean there are not specialised applications where optical processing can make sense, e.g. a matrix multiplication is really just a more complex lens so it's become very popular to make ML accelerators based on this.

[momoschili]

Contrary to the prior commenter, there is definitely significant engineering going toward this, but it's not clear or likely that photonic computing will supplant electronic computing (at least not anytime soon), but rather most seem to think of it as an accelerator for highly parallel tasks. Two major ways people are thinking of achieving this are using lithium niobate devices which mediate nonlinear optical effects via light-matter interaction, and silicon photonic devices with electrically tunable elements. In the past there was a lot of work with III-V semiconductors (GaAs/InAs/GaN/AlN etc) but that seems to have leveled off in favor of lithium niobate.

Photonics has definitely proved itself in communications and linear computing, but still has a way to in terms of general (nonlinear) compute.

[ls612]

Yeah that was sorta what I was thinking is there a clever way to exploit light interacting with matter to turn the gate on/off.