# Can light be rotated using lenses or prisms?

I was wondering if it was possible, by using only lenses, mirrors, or prisms, to rotate a ray of light coming from a certain direction. For example, if I have two lasers beams side by side, is it possible that after going through an optical setup, that the laser beams appear one on top of each other? I don't want to use stuff like optical fibers or electronics, I just wish to know if it is possible to do it with purely optical devices.

• What would it mean to "rotate a ray of light?" Are you maybe asking about how to rotate an image? There are various ways in which a prism (or system of prisms) can be used to rotate an image by a fixed or variable amount. (e.g., en.wikipedia.org/wiki/Dove_prism en.wikipedia.org/wiki/Porro_prism – Solomon Slow Jan 18 '16 at 2:15
• Yes, I suppose I wanted to say "rotate an image". The Dove prism is exactly what I was looking for, thanks. – Ermir Jan 18 '16 at 2:28
Yes you can. Moreover, you don't need any lenses and such things, you only need a medium with Refractive index $n(\vec r)$. Using Fermat's principle (https://en.wikipedia.org/wiki/Fermat%27s_principle) you can calculate the path of the light travelling through a medium with $n(\vec r)$. You just have to choose a proper $n(\vec r)$ function.