I found a technique, i did not consider earlier.
I think prisms are suited for this domain. An optical wave is split in two. One part is used to illuminate a sample from the bottom with a plane wave. The other part illuminates the sample at a specific point. The waves interfere and the reflected light is measured by a camera. A prism could be used to to scan this spot. It would require a very fast camera but these do exist.
It can be used in reverse as well for triggering reactions like polymerization. This requires something like a digital micromirror device, these are typically slower. So that might not be a good fit with current technology.
There is a very nice old video on holography on YouTube