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First Silicon Laser
An anonymous reader writes "Since the creation of the first working laser, scientists have fashioned them from substances ranging from neon to sapphire. Silicon was not considered a candidate, because its structure wouldn't allow for the proper line-up of electrons needed to get this semiconductor to emit light. That has now changed thanks to three researchers at Brown University who have created the first directly pumped silicon laser by drilling billions of holes in a small bit of silicon using a nanoscale template."
That's the sound of a thousand slashdotters trying to make a "shark with friggin laser beams" joke before I do.
A guy walks into a bar... well, I forgot the joke, but the punchline is that he's an alcoholic.
Brown Team Creates 'Impossible' Silicon Laser
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PROVIDENCE, R.I., Nov. 21 -- Silicon has made its way into everything from computers to cameras. But a silicon laser? Physically impossible -- until now. A Brown University research team led by Jimmy Xu has engineered the first directly pumped silicon laser by changing the structure of the silicon crystal through a novel nanoscale technique.
Since the creation of the first working laser -- a ruby model made in 1960 -- scientists have fashioned these light sources from substances from neon to sapphire. Silicon, however, was not considered a candidate. Its structure would not allow for the proper line-up of electrons needed to get this semiconductor to emit light.
Now a trio of Brown University researchers, led by engineering and physics professor Jimmy Xu, has made the impossible possible. The team has created the first directly pumped silicon laser. They did it by changing the atomic structure of silicon itself. This was accomplished by drilling billions of holes in a small bit of silicon using a nanoscale template. The result: weak but true laser light. Results are published in an advanced online edition of Nature Materials.
The feat is an apt one for Xu, whose Laboratory of Emerging Technologies is also known as the "laboratory of impossible technologies."
"There is fun in defying conventional wisdom," said Xu, "and this work definitely goes against conventional wisdom -- including my own."
For now, though, the possible isn't practical. In order to make his silicon laser commercially viable, Xu said, it must be engineered to be more powerful and to operate at room temperature. (Right now, it works at 200 C below zero.) But a material with the electronic properties of silicon and the optic properties of a laser could be useful in both the electronics and communications industries by helping to make faster, more powerful computers or fiber optic networks.
Xu said that when lasers were invented, they were considered a solution looking for a problem. Now lasers are used to power CD players and barcode scanners, and they can cut everything from slabs of steel to delicate eye tissue during corrective surgery.
"A very new discovery in science eventually finds an application," Xu said. "t will just take years of work to develop the technology."
Light emission from silicon was considered unattainable because of silicon's crystal structure, and electrons necessary for laser action are generated too far away from their "mates." Bridging the distance to make the atomic connection would require just the right "matchmaker" phonon arriving at precisely the right place and time.
In the past, scientists have chemically altered silicon or smashed it into dust-like particles to generate light emission. But more light was naturally lost than created. So Xu and his team tried a new way to tackle the problem. They changed silicon's structure by removing atoms.
This was accomplished by drilling holes in the material. To get the job done, the team created a template, or "mask," of anodized aluminum. About a millimeter square, the mask features billions of tiny holes, all uniformly sized and exactly ordered. Placed over a bit of silicon then bombarded with an ion beam, the mask served as a sort of stencil, punching out precise holes and removing atoms in the process. The silicon atoms then subtly rearranged themselves near the holes to allow for light emission.
The new silicon was tested repeatedly over the course of a year to ensure it met the classical criteria of a laser, such as threshold behavior, optical gain, spectral line-width narrowing and self-collimated and focused light emission.
Another first silicon laser? So who was really first?
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http://oemagazine.com/newscast/2004/102604_newsca
Los Angeles, CA | 26 October 2004 -- Researchers at UCLA have demonstrated the first silicon laser, which could lead to more effective biochemical detection, secure communications, and defense against heat-seeking missiles.
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http://www.intel.com/technology/silicon/sp/
First Continuous Silicon Laser
In a paper published February 17, 2005 by the prestigious scientific journal Nature, Intel researchers disclosed the development of the first continuous wave all-silicon laser using a physical property called the Raman Effect. They built the experimental device using Intel's existing standard CMOS high-volume manufacturing processes. This is the third silicon photonics paper Intel has published in Nature since 2004, beginning with the modulator breakthrough (see the Learn More section).
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http://www.photonics.com/readart.asp?url=readarti
PROVIDENCE, R.I., Nov. 21 -- Silicon has made its way into everything from computers to cameras. But a silicon laser? Physically impossible -- until now. A Brown University research team led by Jimmy Xu has engineered the first directly pumped silicon laser by changing the structure of the silicon crystal through a novel nanoscale technique.
Evil people are out to get you.
First bubbles, now Lasers! Frikin' Lasers!
The eternal struggle of good vs. evil begins within one's self.
But a silicon laser? Physically impossible
Diode lasers use silicon, or at least compounds of silicon. Some details here and here.
Pretty cool, though that this is the "the first directly pumped silicon laser."
Computational Chemistry products and services.
From TFA...
"Right now, it works at 200 C below zero."
It looks like we'll be seeing penguins with laser beams long before sharks with lasers beams.
Currently, putting a practical laser on a chip means using a semiconductor other than silicon, such as gallium arsenide. But silicon has better properties for making large complex circuits - and the technology of doing so is more advanced on silicon than on other semiconductor materials.
This means that when you want to hook up a laser to a logic circuit you end up with two separate chips and interconnections between them (or maybe with a separate layer of the lasing semiconductor grown onto a silicon chip.) This is a major hassle and expensive. It also costs a surprising amount of power to drive high-speed signals through the connection between the two chips.
If it were possible to build the lasers on, and out of, the silicon chip itself it would drastically decrease the cost and power consumption of the resulting devices.
Beyond this, it would be an enabling technology: It costs even more power to push signals between one silicon chip and another across a board or backplane. It would be nice to use a laser and optic fiber to make the connection. But why bother if you still have to spend the power to get the signal through the wiring from the silicon to a separate laser that generates the light? If you could put the laser on the silicon chip and save the power you could replace (at least) the critical high-speed wiring between chips with fibers, drastically increasing speed and cutting power.
Up to now it hasn't been possible to get silicon to lase directly (although there has been some recent work with nanoscale laser structures grown on its surface.) Now they've found a way to do it.
It isn't ready for prime time yet, by a long shot. But it's the initial crack in the wall, and breaking down this wall is a BIG DEAL. So researchers will be jumping on this. You might see additional breakthroughs and practical applications in shorter order than with other new technology breakthroughs.
If they get it working efficiently in the region between room temperature and near boiling point where silicon chips normally operate you'll get another increment in processor speed/power/size tradeoffs.
It's a way to sidestep yet another of the long string of roadblocks that have threatened to knock us off the Moore's Law curve.
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The laser diode you're talking about is not made of silicon...
When did GaAs or GaAn become equivalent to Si?
. htm
From http://www.mtmi.vu.lt/pfk/funkc_dariniai/diod/led
he radiative recombination of electron-hole pairs can be used for the generation of electromagnetic radiation by the electric current in a p-n junction. This effect is called electroluminescence. In a forward-biased p-n junction fabricated from a direct band gap material, such as GaAs or GaN, the recombination of the electron-hole pairs injected into the depletion region causes the emission of electromagnetic radiation. Such a device is called a Light Emitting Diode (LED). If mirrors are provided (usually by cleaved crystallographic surfaces of the semiconductor) and the concentration of the electron hole pairs (called the injection level) exceeds some critical value, this device may function as a semiconductor laser that emits a coherent electromagnetic radiation with all photons in phase with each other. LEDs fabricated from different semiconductors cover a broad range of wavelengths, from infrared to ultraviolet.
The electrical conductivity of a semiconductor can be increased by adding doping elements, or small percentages of impurity elements, to the semiconductor. The presence of the small traces of impurity elements can yield extra charge carriers which are free to move through the material.
In the compound gallium arsenide, each gallium atom has three electrons in its outermost shell of electrons and each arsenic atom has five. This gives an average of four electrons per atom in the compound. When a trace of an impurity element with two outer electrons, such as zinc, is added to the crystal, the result is the shortage of one electron from one of the pairs. This shortage sets up an imbalance in which there is a place in the crystal for an electron but there is no electron available. This is commonly called a "hole." This forms the so-called p-type semiconductor in which the conduction of electricity is by motion of the hole from one atom to another.
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