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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."
Here is the link to the actual article in Science: http://www.sciencemag.org/content/early/2011/12/21/science.1214383
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
http://simple.wikipedia.org/wiki/Diode
http://simple.wikipedia.org/wiki/Logic_gate
All those degrees in looking things up online finally paid off. You're welcome, citizen!
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.
My point was that the signal is the important part. They have no way of switching this optical diode.
The diode effect is fairly irrelevant and unimportant. As a matter of fact, digital logic doesn't require something to act like diode at all: relay logic doesn't use diodes.
Here's what they did, I don't understand a word of it but it was simple enough to google.
And did you exchange a walk on part in the war for a lead role in a cage? - Pink Floyd.
You can't build logic for any given truth table using nothing but diodes. You can only build logic for some truth tables, which doesn't give you programmable digital logic. Happy now?