A breakthrough in nanolaser technology has been made by Arizona State University researchers.
Electrically powered nano-scale lasers have been able to operate effectively only in cold temperatures. Researchers in the field have been striving to enable them to perform reliably at room temperature, a step that would pave the way for their use in a variety of practical applications.
The research team is led by Cun-Zheng Ning, an electrical engineering professor in the School of Electrical, Computer and Energy Engineering, one of ASU’s Ira A. Fulton Schools of Engineering.
He has been among engineers and scientists across the world attempting to fabricate a workable nanolaser with a volume smaller than its wavelength cubed – an intermediate step toward further miniaturization of lasers.
Miniaturizing lasers is crucial to making electronics smaller and better, and enabling them to operate faster. Packing more lasers into smaller spaces is necessary for downsized devices to maintain high performance. Being able to integrate more lasers onto a small microchip would make the next generations of computers faster and smaller. The wavelength scale is the next milestone to be achieved in the overall effort to enable more miniaturization.
Refining the shrinking technique
Ning explains that extremely small and thin lasers have been developed, but they needed to be optically driven by a larger laser. In addition, current electrically driven nanolasers can operate only at low temperatures or and emit light only in short bursts or pulses.
To enable them to be useful in practical applications – particularly for improvements of electronic and photonic technologies – it’s necessary that the laser operates at room temperature without a refrigeration system, that it be powered by a simple battery instead of by another laser, and that it is able to emit light continuously.
“That has been the ultimate goal in the nanolaser research community,” Ning says.
Ning’s team started looking for solutions almost seven years ago, before he joined ASU, with his then- postdoctoral assistant, Alex Maslov, who is currently a scientist with Canon USA Inc.
While working for the National Aeronautics and Space Administration’s Ames Research Center, they proposed a semiconductor wire coated with a silver shell. They showed that such a core-shell structure was able to shrink the nanolaser to an incredibly small scale.
About four years ago, working with Martin Hill, a former professor at Eindhoven University of Technology in the Netherlands, the team developed the thinnest nanolaser capable of operating at low temperatures. Two years ago, with the aid of Ning’s student, Kang Ding, they were able to raise the operating temperature to 260 Kelvin (8.33 degrees Fahrenheit).
More recently the team demonstrated a device that could operate at room temperature (read the article in the journal Physical Review B), but the overheating led to imperfect device operation and a conclusive demonstration of lasing remained elusive.
The most recent results, however, demonstrated an eight-fold improvement over previous results from a year ago, finally providing an unambiguous demonstration of continuous electrically driven operation of a laser at room temperature, Ning says.
To explain the significance of such an advance, Ning says, “Imagine if computers had to be cooled down to minus 200 Celsius (minus 350 degrees Fahrenheit) for our current information technology to work. If that were the case, we would not have the widespread usage of computers and social media.”
With nanolasers that can operate at room temperature and be powered by a simple battery, they can be used to make computers operate faster, significantly broaden Internet bandwidth, and provide light sources for many computer-chip-based sensing and detection technologies.
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