For over 100 years, electronic devices have been regulated by a concept called the Q factor. If the devices are storing a lot of energy for a long time, they need to have a small bandwidth, or vice-versa. This has been a constraint for lasers, electronic circuits, and medical devices – one we thought we couldn’t escape. But we were wrong.
An international team of researchers has developed a way to ignore this Q factor, by creating an asymmetric and non-reciprocal system. This set up has allowed them to supercede the conventional limit of the Q factor by a factor of 1,000 and, as they report in Science, it doesn’t appear there’s a theoretical limit to the time-bandwidth restriction.
"It was a moment of revelation when we discovered that these new structures did not feature any time-bandwidth restriction at all," lead author Kosmas Tsakmakidis, from the University of Ottawa and the Federal Polytechnic School of Lausanne in Switzerland, said in a statement. "These systems are unlike what we have all been accustomed to for decades, and possibly hundreds of years."
The Q factor comes from the physics of resonators, systems that oscillate at specific frequencies due to their properties. A resonator that people might be familiar with is quartz crystals, used in both radio transmitters and quartz watches.
The team constructed a magneto-optic material that acts as a resonator, but doesn’t behave like a classical one. When the magnetic field is applied, the new system can hold a wave and store it, accumulating energy over time.
"Their superior wave-storage capacity performance could really be an enabler for a range of exciting applications in diverse contemporary and more traditional fields of research," Hatice Altug, who leads the research group at the Federal Polytechnic School of Lausanne, added.
Of the potential applications already eyed by researchers, there’s improvement in fiber optics and telecommunications. The team thinks these new resonators could be great optical buffers, devices that store data as it moves through fiber optic systems. Until now, this has been limited.
"The reported breakthrough is completely fundamental – we're giving researchers a new tool. And the number of applications is limited only by one's imagination," concluded Tsakmakidis.
Ideas already touted by a Q-factor-less resonator is on-chip microscopy, which would revolutionize medical devices, ways to store energy, and even broadband optical camouflaging – literally the ability to make an object invisible in optical light. If someday soon you have an invisibility cloak, you know where it all started.
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