I know how beat frequencies work with sound. I know they exist in RF so how do they affect light?
The difficulty is that they need a medium to mix in.
Light doesn't interact with light in air or vacuum (at sensible power levels)
A radio uses beat frequencies to mix the received signal with a carrier in a diode, I can't think of a similair substance for light.
I think it can be done optically using a master oscillator, as a way to stabilize a resonant cavity. Not sure about the equipment- a photodiode of some sort, most likely.
You can generate difference (beat) frequencies by mixing optical signals in a second-order nonlinear medium.
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