There is a Germany Company that manufactures a system with fiberoptic line you instill in a vein. Then connects to an adjustable variable wavy light sourse.
Had been around since 2004
For more context, this is the paper he published. Optogenetic rejuvenation of mitochondrial membrane potential extends C. elegans lifespan | Nature Aging
Vielight has a device that does it through nasal capillaries. Vielight 655 Prime (Systemic) - low level laser PBM device
Edit: they have more than one device. This one uses a different wavelength. The difference should be how deep the light penetrates, but these aren’t very different and they state both have similar efficacy. I think that both hit the underside of the brain as well.
Controlled 590 nm light to optically rejuvenate membrane potential of mitochondria - #4 by Joseph => can we merge threads? I propose merging into the thread whose title has more detail
Finally the breatharians have a shot at making it work.