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Tiny ‘microcomb’ could help discover exoplanets and detect diseases

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PhD Student Óskar Bjarki Helgason demonstrates the chip and the experimental setup for generating the microcomb (Credit for photo: Mia Halleröd Palmgren. Credit for collage: Yen Strandqvist/ Chalmers)
PhD Student Óskar Bjarki Helgason demonstrates the chip and the experimental setup for generating the microcomb (Credit for photo: Mia Halleröd Palmgren. Credit for collage: Yen Strandqvist/ Chalmers)

A tiny new photonic device could be used to find new exoplanets, monitor our health and make the internet more energy efficient, its developers have said.

Researchers from Chalmers University of Technology, Sweden, developed the device, known as a microcomb. They said it “could bring advanced applications closer to reality”.

A microcomb is a photonic device capable of generating a myriad of optical frequencies – colours – on a tiny cavity known as microresonator. These colours are uniformly distributed, so the microcomb behaves like a 'ruler made of light'. The device can be used to measure or generate frequencies with extreme precision.

In a recent article in Nature Photonics, eight Chalmers researchers described a new kind of microcomb on a chip, based on two microresonators. They said the new microcomb is a ‘coherent, tuneable and reproducible’ device with up to ten-times higher net conversion efficiency than the current state of the art.

“The reason why the results are important is that they represent a unique combination of characteristics, in terms of efficiency, low-power operation, and control, that are unprecedented in the field,” said Óskar Bjarki Helgason, a PhD student at the Department of Microtechnology and Nanoscience at Chalmers, and first author of the new article.

The Chalmers researchers are not the first to demonstrate a microcomb on a chip, but they developed a method that overcomes several well-known limitations in the field. The key factor is the use of two optical cavities – microresonators – instead of one. This arrangement results in the unique physical characteristics.

Placed on a chip, the newly developed microcomb is so small that it would fit on the end of a human hair. The gaps between the teeth of the ‘comb’ are very wide, opening up opportunities for researchers and engineers.

Since almost any measurement can be linked to frequency, the microcombs offer a wide range of potential applications. They could, for example, radically decrease the power consumption in optical communication systems, with tens of lasers being replaced by a single chip-scale microcomb in data centre interconnects. They could also be used to measure distance in Lidar systems for autonomous vehicles.

Another area where microcombs could be used is calibration of spectrographs used in astronomical observatories devoted to the discovery of Earth-like exoplanets.

Extremely accurate optical clocks and health-monitoring apps for our mobile phones are further possibilities. By analysing the composition of our exhaled air, they could potentially help diagnose diseases at earlier stages.

“For the technology to be practical and find its use outside the lab, we need to co-integrate additional elements with the microresonators, such as lasers, modulators and control electronics. This is a huge challenge, that requires maybe 5-10 years and an investment in engineering research. But I am convinced that it will happen," said Victor Torres Company, who led the project.

He added: “The most interesting advances and applications are the ones that we have not even conceived of yet. This will likely be enabled by the possibility of having multiple microcombs on the same chip. What could we achieve with tens of microcombs that we cannot do with one?”

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Content published by Professional Engineering does not necessarily represent the views of the Institution of Mechanical Engineers.


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