Question: How do lasers work and how do you create them?

Bruce Saleeb-Mousa answered on 13 Mar 2020:

The most common lasers (like laser pens) are made using a special type of material called a semiconductor. This material allows electricity to pass through it in certain situations but not in others. We can grow stacks of this material, on layer on top of another. By carefully choosing the thickness of each layer and the amount of each different semiconductor material in each layer, we can build lasers of many different colours.

The way the laser works is we apply electricity through this stack of materials which causes small packets of light to be spontaneously made in the middle. These packets of light then can travel up or down the stack and get reflected back into the centre since the stack acts like two mirrors pointing to the centre. The packets of light which then get reflected back into the centre then cause more packets of light to be made. This happens over and over and the strength of the light builds up. Eventually the light escapes out the edge of the material and this is the laser light you see coming out of your laser pen. We have to be careful with laser light though as it has a lot of energy and can damage our eyes.