MIT team applies microwave beam-forming techniques to micro-laser arrays

June 15, 2016 // By Graham Prophet
Researchers at MIT and Sandia National Laboratories have designed a device that is an array of 37 microfabricated lasers on a single chip. Its power requirements are relatively low because the radiation emitted by all of the lasers is phase locked.

The development, say the researchers, represents anew approach to microlasers, with the prospect of using such arrays in, among other applications, terahertz security scanners – terahertz meaing the spectral interval between microwaves and visible light. Diagnostic or security applications in that area would require compact, low-power, high-quality terahertz lasers.

 

In Nature Photonics, the researchers at MIT and Sandia National Laboratories describe a new way to build terahertz lasers that could significantly reduce their power consumption and size, while also enabling them to emit tighter beams, a crucial requirement for most practical applications. The work also represents a fundamentally new approach to laser design, which could have ramifications for visible-light lasers as well.

 

In their paper, the researchers identified four previous phase-locking techniques, but all have drawbacks at the microscale. Some require positioning photonic components so closely together that they would be difficult to manufacture. Others require additional off-chip photonic components that would have to be precisely positioned relative to the lasers. Hu and his colleagues’ arrays, by contrast, are monolithic.

 

“This whole work is inspired by antenna engineering technology,” says Qing Hu, a distinguished professor of electrical engineering and computer science at MIT, whose group led the new work. “We’re working on lasers, and usually people compartmentalize that as photonics. And microwave engineering is really a different community, and they have a very different mindset. We really were inspired by microwave-engineer technology in a very thoughtful way and achieved something that is totally conceptually new.”

 

In Hu and his colleagues’ array, each laser generates an electromagnetic field that induces a current in the lasers around it, which synchronizes the phase of the radiation they emit. This approach exploits what had previously been seen as a drawback in small lasers. Chip-scale lasers have been an active area of research for decades, for potential applications in chip-to-chip communication inside computers and in environmental and biochemical sensing. But as