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Passive Optical Diode Created At Purdue University
wbr1 writes "Researchers at Purdue University have managed to create a silicon device that acts as a passive diode for infrared optical signals. From the Purdue news release: 'The diode is capable of "nonreciprocal transmission," meaning it transmits signals in only one direction, making it capable of information processing, said Minghao Qi (pronounced Chee), an associate professor of electrical and computer engineering at Purdue University. "This one-way transmission is the most fundamental part of a logic circuit, so our diodes open the door to optical information processing," said Qi.' One of the same researchers had already (using similar technology) created a way to convert laser pulses to RF."
Both the summary and TFA are devoid of anything concrete on how this is actually done. It basically says what the title does, they created a diode. Telling me that light entering the opposite side doesn't make it through really doesn't tell me anything the word "diode" in the title doesn't. I'm sure the science behind this particular device is both clever and interesting but you'd never be able to tell since that information is completely missing. Reporting on stories is nice, but shouldn't journalists actually strive to make their articles contain actual information on what they are covering? You'd think a story about a new discovery would actually contain information about how it actually works (since that's the actual "new" part anyway).
Entropy is always free. The Universe has been doing it without charge for billions of years.
I have something in common with Stephen Hawking...
Infrared light is not heat. I don't know where people got this idea. It is light. When it is absorbed, it may cause certain molecules to gain heat energy, but it is still light. This is a device which absorbs or scatters when you shine light on one side of it, and transmits when you shine light on the other side of it. I assume when heat energy is generated within the device, it diffuses isotropically from the point of matter-light interaction throughout the material until a definite temperature is reached, as thermodynamics predicts. If you believe that materials with different absorption cross sections at different spatial orientations allow you to violate the second law of thermodynamics, then you hardly need to construct something so elaborate: a board painted two different colors on either side should suffice. Lasers themselves, whose cavities emit a lot more in one direction than in the other (and which generate a good deal of heat in their lasing medium in a largely homogeneous fashion, but let's not get bogged down in reality) should constitute a huge violation. You should let everyone in the physics community know, as this seems like a fairly large oversight in our model of reality /sarcasm
If you're going to go around with a name like physburn, please ensure you understand what you're talking about
A transistor acts as an electrical switch. Basically, it means that when an input is provided, the rest of the circuit can do something, but at the same time the input is electrically isolated from the rest of the circuit.
Before transistors, there were relays and tubes which accomplished the same thing. They were slower, larger, hotter, and used a lot more electricity. And they were prone to burning out. As a result, computers were hopelessly complicated, the size of small rooms, and were programmed with a screwdriver. And "bugs" in the computer program were sometimes, literally, bugs. A moth, in at least one story. And an IBM chairman famously stated that he saw a world-wide market for about 5 computers.
Then the digital transistor came along and revolutionized that. They were smaller, faster, and required much less power. And they were cheaper, too. The integrated circuit - millions of transistors etched onto a single silicon die - revolutionized that further.
A transistor also acts like a diode, in that it only lets current flow in one direction. But note that this isn't really even necessary: relays, for instance, didn't prevent current from flowing backward. The main thing is that the input is electrically isolated from the output, not that it allows current to flow in only one direction.
So basically, they have everything required to build an optical transistor, except for the switching part. Which is kind of the more important part anyway.