Turning metals into insulators and back again

It is well-known that metals conduct electricity and that insulators prevent its flow, but imagine being able to change a material from a metal to an insulator and back again using only light. The ability to do this would be incredibly useful for making ultrafast optoelectronic devices for advanced computing applications. Some materials have shown the ability to switch from insulators to metals under light pulses. However, it is much more difficult to perform the reverse change from a metal to an insulator.