A new laser paradigm: An electrically injected polariton laser

May 15, 2013, University of Michigan

Engineering researchers at the University of Michigan have demonstrated a paradigm-shifting "polariton" laser that's fueled not by light, but by electricity.

Polaritons are particles that are part light, and part matter.

"We report the first electrically injected polariton laser—a truly transformative result," said Pallab Bhattacharya, the Charles M. Vest Distinguished University Professor of Electrical Engineering and Computer Science and the James R. Mellor Professor of Engineering, whose paper on the work is published online in Physical Review Letters.

"Since the proposal of such a device in 1996, researchers around the world have been trying to demonstrate it. It is no longer a scientific curiosity. It's a real device."

The new device requires at least 1,000 times less energy to operate, compared with a conventional laser, Bhattacharya says. He envisions its eventual use in any application where a laser is used today, such as in the optical communication field for wired Internet and in the for surgery.

And as transistors—the building blocks of computers—reach their fundamental size limit over the coming decade, Bhattacharya says lasers like this one that are low-power and easier to modulate could play new roles in consumer electronics.

"Some of the communication on the chip and from chip to chip is going to move to , or lasers," Bhattacharya said.

Technically, "laser" is a for the new device. The word is actually an acronym for Light Amplification by Stimulated Emission of Radiation. A polariton laser produces a of light in a different way.

"The physical process is Light Amplification by Stimulated Scattering of Polaritons," Bhattacharya said.

The researchers generated polaritons by using electricity to excite samples of the semiconductor in a microcavity under certain conditions. The polaritons quickly decayed by transferring their energy to photons, which, due to properties of the original polaritons, escaped the cavity as a single-colored .

"Our success is based on two novel features," Bhattacharya said. "First, we deployed additional electron-polariton scattering to enhance the relaxation of polaritons to form the coherent ground state. Second, we applied a magnetic field so that more carriers can be injected with the bias current without losing the required conditions for polariton lasing."

This laser must be at cryogenic temperatures to operate, but Bhattacharya and his colleagues are working on a room temperature version.

Explore further: Advancing secure communications: A better single-photon emitter for quantum cryptography

More information: prl.aps.org/accepted/fb072YbfJ … b39e528d354fabd828bd

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3 / 5 (2) May 15, 2013
Initially, I expect the military will be looking at this for obvious applications.

Commercially or industrially; I wonder if this technique could be useful for heavy plate cutting such as in ship building and mold tool plate cutting. "1,000 times less energy to operate" is a big deal and may allow for miniaturization of present equipment.
1.8 / 5 (5) May 15, 2013
I wonder if this technique could be useful for heavy plate cutting such as in ship building and mold tool plate cutting. "1,000 times less energy to operate" is a big deal and may allow for miniaturization of present equipment.

It could be a really big deal if so; I recently read this in another article:

"The electricity used in building a car is about 20 percent of the cost of the structure," said Marcilio Alves, an engineering professor at Brazil's premier University of Sao Paulo and one of the few independent researchers in the nation looking at car safety.

Makes you wonder how much money is spent on electricity when building a huge ship.
5 / 5 (1) May 15, 2013
> This laser must be at cryogenic temperatures to operate

Ok. That reminds me of the MASER. During a long time it remained a laboratory curiosity, just because of the low temperature requirement.
1 / 5 (4) May 17, 2013
Back in 2007 they did this at room temperature using Gallium Nitride and optical injection.
Perhaps this new electrical injection system would work there too.
And it's only 1000 times better if you want it 1000 times less bright. As it doesn't need pumping, to get a population inversion, to lase. It's not a death star in the making but it could make photonics optical communication use less power.

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