[ganzuul]

A diffraction grating made up by free electrons could do it. Alternatively total internal reflection by heating a volume with a phased array.

At least that's how we used to do it a long, long time ago.

[actionfromafar]

were you far away?

[r2_pilot]

Considering how long free electron lasers have to be for the wigglers to work, I'd imagine so. But if you can get electrons to oscillate fast enough in a small enough distance, hit me up.