Visible light

Interesting and fascinating topic!
I forget now which website or forum I saw this on around 2017, but this was the answerer's generalized reply (extracted notes from screenshots as printing/saving was disabled):

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Although electrical EM radiation and visible light may theoretically be made to oscillate at the same frequency, say 500 Terahertz, the radiated format of each is independant of the other.
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At theoretical 500 THz, an electrically radiated waveform would be an electrical signal, oscillating at 500 THz, but as light photons do not react with relatively weak magnetic fields, it's not likely that this high frequency "radio" signal would produce artificial "light" though the media.
More likely, it could be a potential (future) weather-modification "cannon", military applications, or super-fast communications platform.
Put another way, if sound waves are transmitted through air at 1MHz, you will get 1MHz ultrasonic audio, not RF, even though they fall within the same frequency range.
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Although direct electrical oscillation at light wavelengths (around 0.5um) is not yet feasible, electro-chemical junctions can produce light (LED, Laser, etc).

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(My added penny): I gather from above notes that they emit light, but not generate the oscillations....

 

For an oscillator to work at the frequency of light, it would have to be smaller than the wavelength of that light, otherwise the signal could not get from the output to the input in time.

Bob