Wireless laser power transmission using a gain medium between retroreflectors | Hacker News Reader

Wireless laser power transmission using a gain medium between retroreflectors

patents.google.com

24 pointsvinnyglennon13 comments

I don't see how you can use a retroreflector as one end of a laser cavity. They destroy coherence, since the path length is different depending on where each photon hits the reflective element. Don't lasing mediums require fairly coherent photons for stimulated emission to work?

I don't think this will be a problem. A classic gas laser can have variations of more than 1 wavelength in its cavity without any issues. I believe this was one reason for the relatively short coherence length of HeNe lasers, but I could be wrong.

I bet you the lasers in these transmitting devices will not be gas but small solid state units. As this becomes more popular, like surface-mount camera dies, these SMD IR laser diodes will become smaller and smaller.

They are probably using semiconductor units (with lasers "solid-state" usually refers to non-semiconductor solid lasers, such as ruby lasers). My point with HeNe lasers was that having variations in the cavity length is not a problem for lasing.

I think the path length may be constant. Retroreflectors can be used in Michelson interferometers.

https://patents.google.com/patent/US5309217

I stand corrected.

Not clear how this couldn't inadvertently fry my eyeballs. Even very low-powered IR lasers are regulated because there is no blink-reflex.

Read the patent or watch the video https://www.youtube.com/watch?v=YeNXRD8eziA&t=0s

In simple terms, the laser transmitter, the laser receiver and the beam that is used introduces a feedback mechanism that the transmitter can employ to immediately detect an unsafe condition and cut the high power (infra red) laser transmission. The response is so fast that the risks to damaging eyes, etc are acceptably low.

I'm still trying to figure out how that would work with e.g. a piece of glass sitting at an angle other than parallel to the wavefront. That would pass most of the light while reflecting a collimated beam that is much more powerful than allowed for direct laser emission.

Consider the situation where a flat piece of lime glass is in the way at an angle that reflects 1% of the light and passes the rest. With a 3W beam, that would reflect 30mW of laser light which as a direct emitter would be class 3B.

I'm more confident now that it's probably very dangerous and may not get the FDA approval. If they do it will be trickle charging. https://www.youtube.com/watch?v=2bXjn3wwM8o

wireless power exists already? Is this the same tech:

https://www.youtube.com/watch?v=YeNXRD8eziA&t=0s

Yeah, the patent filer is WI-Charge Ltd., the company in the video.

Agreed. This is exactly the implementation described in the patent.

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