
Wireless laser power transmission using a gain medium between retroreflectors - vinnyglennon
https://patents.google.com/patent/US20170373543A1/en
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tlb
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?

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analog31
I think the path length may be constant. Retroreflectors can be used in
Michelson interferometers.

[https://patents.google.com/patent/US5309217](https://patents.google.com/patent/US5309217)

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tlb
I stand corrected.

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aidenn0
Not clear how this couldn't inadvertently fry my eyeballs. Even very low-
powered IR lasers are regulated because there is no blink-reflex.

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

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aidenn0
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.

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cottsak
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](https://www.youtube.com/watch?v=2bXjn3wwM8o)

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stevemk14ebr
wireless power exists already? Is this the same tech:

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

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

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

