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calmond writes:
"Researchers from the University of Michigan have created a super-thin light detector that can pick up the entire infrared spectrum in addition to visible and ultraviolet light. The heat vision technology is made of graphene, which is considered to be the world's strongest material, and is small enough to fit on a contact lens.
Its developers say the technology could one day give people super-human vision and is particularly relevant for use by the military. Other, non-military uses, such as checking power distribution cables or search-and-rescue tasks are also possible.
A news release from the University team is to be found here, while a technical abstract is here. Unfortunately, the full technical paper is only viewable by payment or membership.
(Score: 5, Informative) by hubie on Thursday March 20 2014, @03:43PM
Ok, so that is what a press release is supposed to do, but I've looked at the full paper and there are a few disconnects between the paper and the press release. There is mention of covering the full IR spectrum, but the paper only went out to the mid-IR. Graphene can potentially be used as a detector for the far-IR, but I didn't see any mention as to how well it would perform. What was disappointing for me is that the PR and paper mention broadband, but I didn't see any figure that shows the spectral response, or quantum efficiency [wikipedia.org] (QE) curve. This tells you how well it responds over its operating spectrum, and thus lets you know whether it is useful for what you want to use it for. Maybe one can pull it out of the figures in the paper, but it wasn't obvious what the signal to noise would be.
The PR mentioned possibly implanting this on the cornea, but that makes no sense to me. This wouldn't allow you to directly see in that sense, you would still need to have readout circuitry to make you an image; this would be like saying if you mounted a CCD sensor to your eye, it would allow you to see what the sensor sees. However you fix the sensor, you'd still need to project its image onto some kind of heads-up display for you to see it.
(Score: 2, Informative) by JohnnyComputer on Thursday March 20 2014, @05:12PM
Very typical, i.e. so so true.
(Score: 5, Informative) by bd on Thursday March 20 2014, @05:15PM
Well, they do explicitly give you the responsivity at 1300 nm, 2100 nm and 3200 nm in the paper. From that, you can easily calculate the responsivity from R=\eta\frac{e}{h\nu}
I get:
1300 nm: \eta=3.8
2100 nm: \eta=1.12
3200 nm: \eta=0.43
So this device doesn't really have internal amplification after 2100 nm. What I am puzzled by is the time response curve in figure 2. That looks like some _slow_ dynamics going on there.
(Score: 3, Informative) by hubie on Thursday March 20 2014, @06:53PM
I'm still having a hard time getting my head wrapped around this. It looks like the visible data in Figure 2 use a Ta2O5 tunneling barrier, but the IR data in Figure 4 use a silicon barrier. I'm trying to put this in the context of what would the response be for a single broadband device (as hinted at in the press release), and I don't think you can get there from the paper. Also, unless there is some dramatic rise in the QE, it is dropping pretty fast by the time you get to 3200 nm, and so I wouldn't expect it to be too great at 5000 nm for the MWIR, and it would be awfully small out in the LWIR.
I don't know anything about growing graphene layers so I also wonder what the limitations are on making pixelated detectors. Can you make an array of these with unit cells comparable to what you can with silicon and InGaAs?
(Score: 5, Interesting) by bd on Thursday March 20 2014, @09:24PM
Yeah, I am a bit disappointed with the quality of the paper. Especially that they did not go below 1300 nm in the device with the Si barrier. I guess below 1100 nm the photons are above the band gap of the barrier and something funny happens with the device. Maybe not, but if they don't demonstrate it, I'm not convinced. That would leave us with a slow photo-detector that is not that impressive at all...
The press release really reads like a bad peace of science fiction.
(Score: 0) by Anonymous Coward on Friday March 21 2014, @05:02AM
I loved the part where the IB Times article said:
"The heat vision technology is made of graphene, which is considered to be the world's strongest material, and is small enough to fit on a contact lens."
That's a priceless non-sequitur. It's like saying "plastic is small enough to fit on a contact lens."