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Conundrum

Sun Dec 30 2012, 01:36PM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4061

Hi all.
Read something interesting suggesting that a new approach in generating 10.6um (far infrared) using semiconductors much like an LED combined with a plastic encapsulated upconverter using quantum dots at the Rx end could allow a cheap silicon solar cell to be used as a receiver.

Essentially the emitter is a bit like a conventional GaAs LED but they dope it with quantum dots, another variant uses EL to emit broadband infrared instead of visible light which is then collimated into a beam slightly larger than the receiver for safety.

Has anyone else ever run into this?

-A

Carbon_Rod

Mon Dec 31 2012, 12:05AM

Registered Member #65 Joined: Thu Feb 09 2006, 06:43AM
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Posts: 1155

There was a TED talk with a fellow who thinks every window should be a transparent point-to-point directional power transceiver in the mm bands, and people should carry self powered cell phones. I happen to endure the ludicrous presentation as it contained some empirical data of interest.... refused to cite the "fringe theory" talk for obvious reasons.

However, there is a new generation of practical femto-power radio transceivers on the way:

In terms of distance, it is still constrained by the same traditional broadcast propagation models.

lightlinked

Mon Dec 31 2012, 07:59AM

Registered Member #2087 Joined: Tue Apr 21 2009, 08:32AM
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Posts: 115

is it safe to be bombarded with that kind and that much energy?

Nik

Mon Dec 31 2012, 05:16PM

Registered Member #53 Joined: Thu Feb 09 2006, 04:31AM
Location: Ontario, Canada
Posts: 638

If its in far infra red there's no danger at all. You might feel a little warm but that's only if you get into the 1kw/m^2 range and higher. (About what you feel from the sun)

Conundrum

Tue Jan 01 2013, 02:04AM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4061

Plus the receiver would make an excellent solar cell, at least in the summer months.
Don't forget that some 40% of the Sun's energy is emitted in the infrared bands.

lightlinked

Tue Jan 01 2013, 03:31AM

Registered Member #2087 Joined: Tue Apr 21 2009, 08:32AM
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Posts: 115

how much of this stuff do we get from the sun? I mean you might not be able to see an IR laser but you definitely can get blinded by one, ie CO2 lasers for cutting or diode pumping lasers. but that is near IR vs. far IR. sort of like 2.4 GHz in your phones wifi radio vs. 2.4 GHZ out of a microwave oven.
Is it supposed to be more efficient than a traditional solar cell being blasted by a traditional IR laser? I mean in terms of energy transfer and conversion obviously that much IR at say, 1064nm, is bad for your eyes where as IF the same amount of far IR is okay to be exposed to than its not a problem.
either way quantum dots on solar cells is a win win.

Conundrum

Tue Jan 01 2013, 09:19AM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4061

I think the plan is to use an incoherent i.e. LED like beam, lasers would be fine for very large distance i.e. space use though.

Carbon_Rod

Tue Jan 01 2013, 10:30AM

Registered Member #65 Joined: Thu Feb 09 2006, 06:43AM
Location:
Posts: 1155

lightlinked wrote ...

is it safe to be bombarded with that kind and that much energy?

@lightlinked
The TSA scanners operate in this band, and people are very unhappy to see a safety study on the technology. Ignoring energy potential of shorter wavelengths, note exposure in upper GHz to IR do not trigger a human iris response to intense light. And therefore, minimal exposure to even a small laser in IR could cook the color vision out of your eyes over time.

Additionally, even at 1064nm most things like paper or skin are transparent, and a coherent beam would penetrate several inches into the body.

@Conundrum
That "warm feeling" you get from a deep radiation burn only tells part of the story, and takes a long time to heal.

@Nik
Safety is often a statistical argument these days...

Conundrum

Tue Jan 01 2013, 01:05PM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4061

10.6um is 10600nm not 1064.

Its closer to heat than light, the eye does absorb this wavelength but only in the surface layers.
Sitting near a coal fire doesen't seem to cause a problem, in fact those "infrared" heaters put out hundreds of watts and no epidemics of blindness or cooked skin.

Carbon_Rod

Wed Jan 02 2013, 07:33AM

Registered Member #65 Joined: Thu Feb 09 2006, 06:43AM
Location:
Posts: 1155

Ocular injuries caused by exposure to wavelengths much longer than 10.6um are also well documented. I'm not too clear what the nm conversion of another area of the spectrum offers to the peer reviewed publications.

Perhaps my denotative verbosity has deteriorated with time...

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