A team of applied physicists has devised a method to develop the world's smallest light-powered gyroscope — a fraction of the width of a human hair — that will enable a new generation of phenomenally compact gyroscope-based navigation systems, among other intriguing applications.
"We have found a new detection scheme that may lead to the world's smallest gyroscope sooner," said Li Ge, physicist at the City University of New York.
More than creative learning toys, gyroscopes are indispensable components in a number of technologies, including inertial guidance systems, which monitor an object's motion and orientation.
Space probes, satellites and rockets continuously rely on these systems for accurate flight control.
Optical gyroscopes have no moving parts. Instead, dual light waves race around an optical cavity or fibre, constantly passing each other as they travel in opposite directions.
After directly measuring the colour change of the light waves, the researchers determined that they could measure the pattern the light produced as it exited the cavity.
"That was our key innovation — finding a new signal with a much improved sensitivity to rotation," said Ge, who conducted the study with physicist Hui Cao and her student Raktim Sarma, both at Yale University in New Haven.
Traditionally, engineers have used two approaches to make optical gyroscopes, both based on the Sagnac effect which creates a measurable interference pattern when light waves split and then recombine upon leaving a spinning system.
The first one uses an optical cavity - an engineered structure on a crystal - to confine light and the second one uses an optical fibre to guide light. The second approach has, to date, been most practical because its sensitivity can be easily enhanced by using longer sections of optical fibre (some up to five kilometres long).
Though this system is sensitive to rotation, there are practical limits to how long the fibre can be and how small it can be wrapped before the fibre itself is damaged.
The problem, however, has been that the sensitivity of this type of optical gyroscopes degrades as the cavity gets smaller.
According to researchers, further studies are needed to take into consideration the possibility that many modes, or light paths, exist simultaneously in the cavity.
The study was published in The Optical Society's (OSA) new journal Optica.
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