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It's not impossible:

Lasers have been used for 50+ years in the intelligence community to eavesdrop on voice conversations.

My understanding is that light doesn't interact with electromagnetic fields, so you couldn't use a laser to detect electromagnetic fields.

light IS a EM field. First sentence on wiki: "Light is electromagnetic radiation ..."

And yes, electromagnetic fields interact.

You're probably thinking of a directed antenna, something like the BlueSniper rifle that was all the news like 10 years ago...

Consider a physics class to learn about electricity and magnetism.