Isn't that what a television or monitor does?

No they use three different color lights and mix them at different intensities and it looks to our eye like that color. What I mean is why can't we create arbitrary, single frequency colored lights when we can do that with radio waves? Is it just because we don't know how to do it in that range?

When you make radio waves, you're charging already existing electrons in the air to make them wiggle. As I understand it, photons are emitted by electrons when those electrons wiggle in a very specific way, so when you make light you have the added step of inducing photon emission in the electron. So like instead of wiggling the electron the right way you have to get the electron to release a photon that's wiggling the right way.

This is what diodes do. For a while it was really tough to manufacture diodes that produced blue light. I assume this has something to do with accuracy of manufacturing processes.

Now we have smart LED light bulbs and you basically can set them to produce arbitrary colors of visible light lol. So I guess we're there or close enough to there already.

This is what a laser does, through "stimulated emission" (i am not joking, that is what it's called) of electromagnetic radiation!

Also look into "masers" or "spasers".

But other than that, no idea. I speculate it's really difficult to do that within the ~500 terahertz frequency (visible light?) Wifi radiation is at ~5 gigahertz and radios are at ~kilohertz.

All the light emitters I know of use fixed-frequency emitters. Phoshpors, etc.

https://en.wikipedia.org/wiki/Tunable_laser It seems there are some "tunable lasers", and reading on these shows me some (new!) research into tunable phosphors: https://pubs.rsc.org/en/content/articlelanding/2018/dt/c8dt01991f

The abstract cites displays as an example!

I like this question!

Because colours aren't frequencies of light, they are perceptions that are created by our bodies. We perceive colour when cone cells in our eyes react to light. There are three different kinds and they each have ranges of frequencies that stimulate them. We call them red, blue and green cones and thus perceive those as "primary colours" but the frequency ranges that stimulate the different cells actually overlap a lot, especially the red and green ones.

Any colour you perceive is the result of the different cones in your eyes being stimulated by different amounts, and you see different colours based on how much each is stimulated. And many colours that we perceive correspond to mixes of stimulation level across the cones that can only happen when they are stimulated simultaneously by different frequencies of light.

There is no single frequency of light that will stimulate the different types of cones in the correct levels for you to perceive magenta, that only occurs if there is a mix of frequencies hitting your eyes that stimulate the blue and red cones a lot without stimulating the green cones, and as the green cone range lies somewhere in between the red and blue cone range that can't happen with a single frequency.

There is no single frequency of light that will stimulate the different types of cones in the correct levels for you to perceive magenta, that only occurs if there is a mix of frequencies hitting your eyes that stimulate the blue and red cones a lot without stimulating the green cones, and as the green cone range lies somewhere in between the red and blue cone range that can't happen with a single frequency.

That I know. It's more a question of why we can't create light at arbitrary wavelengths, not why we can't create any given color using only a single wavelength.

This is the question I had! Nice! Thank you!

I always thought a laser was special just because all the photons were in the same orientation and so they didn't cause interference from one another, so it appeared more intense and stayed in a tight beam. I did not know you could also in theory use them to create different wavelengths.

This is what a laser does, through "stimulated emission" (i am not joking, that is what it's called) of electromagnetic radiation!

lasers are jizzing light bulbs. got it.

I don't know a lot about lasers and orientation!

But yeah, tunable lasers cost a lot of money. Like, price-not-listed-call-us-for-a-quote prices. As I understand, argon ion lasers could emit most of the frequency spectrum.

Definitely going to revisit this thread if I happen to run into someone who knows more lol