I immediately thought of the old crystal radios and a short search brought up this comparison. While old radios used a natural mineral (galena) to detect radio waves, modern Rydberg radio receivers use a synthetic photonic crystal (often made of silicon or glass) to guide and enhance the radio signal for improved performance.

That's not the function of the crystal though, it is not optical but 100% electrical and serves to demodulate the signal, not to receive it.

https://www.mpg.de/9142418/magnetism-in-artificial-crystal and this