Optical switches are not a contender for general computing. Scaling beyond the diffraction limit (approximately half the wavelength) requires plasmonics, which

Optical switches are not a contender for general computing. Scaling beyond the diffraction limit (approximately half the wavelength) requires plasmonics, which is arguably more lossy than traditional transistors. If anything ever subplants CMOS, it will still likely be based on electron transport. Electrons have a lot of great properties for switching. They are massive enough to be localizable into small spaces, but light enough to be cheap (energy-wise) to accelerate up to high speeds. They are ubiquitous, and they interact strongly with matter, electric fields, and magnetic fields. Light is great for signal transport over long distances in a large part because it interacts so weakly with matter. But that same property makes it difficult to switch.