There have been successful experiments in modulating sound over a carrier ultrasound wave. Not so long ago, I've even seen an DIY implementation on Hackaday.
I also encountered and tested a program that would modulate FM wave over a high-frequency PWM signal.
I don't remember much of the background math but my layman observation is that if you could draw a sinusoidal wave over a signal, then for all purposes the wave is there.
My question is then if you could do the same thing with a completely normal laser beam. That is, change the beam intensity as to form a FM wave over the visible light wave.
This picture kinda illustrates what I mean, not to scale:
The purple line is the frequency of the laser beam (as I said, it's not to scale) and the red line is the intended signal transmission, which is driven by some circuit powering the laser.
The idea the is that the laser beam should demodulate into the FM signal on the target. But I can't really imagine that happening at all.
If this isn't possible, and I think so, why exactly does it work with ultrasound but not a laser?