About 20 years ago the CS community was getting excited about optical memory. It promised to be huge, must faster than static RAM, and hold it's state. Tied directly to the CPU as a very large cache+RAM replacement it would have revolutionized computing. There were other advantages besides speed. One was that you could just pause the CPU, put the computer to sleep, then wake it up later and everything was already in RAM and computation would continue where it left off. Instant boot. Running apps would be instant, they were already in RAM and could be run in place. Prototypes existed but optical memory never happened commercially. Not sure I remember why, maybe couldn't scale, or manufacturing problems. There was also the problem that code is never perfect, so what to do when something stored became corrupted? Without a boot phase there would be no integrity checks.