[frozenport]

Basically in the optical regime it won't be possible to propagate the E field in a conduit smaller than the wavelength. This is because a small conduit doesn't have the right boundary conditions to support fields (like trying to fit waves into a didgeridoo). So you're always going to have these massive, massive 1um structures compare to state-of-the-art nm scale semiconductors.

There are advantages of optics including that light moves faster than electrons (important for HPC where the figure of merit is latency in us between nodes, etc) and typically has higher fidelity. But the size of these structures is orders of magnitude larger than conventional semiconductors.