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Low-Power Laser Could Speed CPUs

The polariton laser now runs on electricity, operates at room temperature, and could be key to on-chip optical interconnects

3 min read
Low-Power Laser Could Speed CPUs
Reflected Glory: University of Michigan engineers built a polariton laser (triangle) that runs on electricity and operates at room temperature. The key was to lower the resistance of the device’s reflectors.
Image: University of Michigan

Lasers have largely replaced the copper wiring of old to speedily stream bits among servers in large data centers. Engineers have long dreamed that they could use lasers to do the same within the servers’ data-congested processors, too. One problem standing in their way is that even the most efficient lasers need an awful lot of current before they light up. But a new kind of device, the polariton laser, could light the way using merely a trickle of electrons. Until recently, however, the device has worked only in an impractical environment.

Now, researchers at the University of Michigan have built the first polariton laser that both runs on electricity and operates at room temperature. It emits coherent light when provided with a current of only 169 amperes per square centimeter. A similar structure operating as an ordinary laser would take more than 250 times as much current, and even the best gallium nitride laser, enhanced with quantum dots, requires at least 1000 A/cm2 before it starts lasing.

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The Transistor at 75

The past, present, and future of the modern world’s most important invention

2 min read
A photo of a birthday cake with 75 written on it.
Lisa Sheehan
LightGreen

Seventy-five years is a long time. It’s so long that most of us don’t remember a time before the transistor, and long enough for many engineers to have devoted entire careers to its use and development. In honor of this most important of technological achievements, this issue’s package of articles explores the transistor’s historical journey and potential future.

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