For some reason sometimes when I make lasers, photon will shoot out at odd angles. Why does this happen and how can I fix this? Here is an example of when it happens : https://powdertoy.co.uk/Browse/View.html?ID=1814533 and I managed to fix it by placing some void near the end like in this save: https://powdertoy.co.uk/Browse/View.html?ID=1814519. But in other lasers I've tried, void doesn't always work.
You should in general make the void about 3 pixels thick to avoid the problem. Basically it has to do with the speed of phot.