Imagine a full light transistor . With the base collector emitter working simultaneously as a light valve, This valve will work on light, letting it pass through or not, it will depend if the gate is charged.
the idea is to create a way to switch on or off a structure based on silicon that can enable light to pass through or hold it and spread as a light bulb.
Now imagine a bunch of this micro phototransistors inside a glass . Using lasers we may be able to switch the transistors and with other laser rgb we will be able to make the color appears where we want.