To your earlier comment about laser printers creating heat, laser printers use lasers hundreds of times more powerful than any laser that would be used in an optical chip. Also, silicon circuits, holding electricity and passing it along by conductivity, allows for some energy to escape in the form of heat, thus causing the chips to become warm. An optical chip, however, wouldn't lose near as much energy to heat (most wasted energy would instead be lost as light), but if the lasers, packed together, did create quite a bit of heat, I doubt it would be much more than any of today's silicon processors.

As for the speed of computing, there will always be programs that can push the limits of a processor. As was said, though, one could always upgrade a computer by simply giving the processor more and more cores, thus breaking down the task and increasing the overall efficiency/speed.