Nanophotonic optical gyroscope on rice grains

Rice grains dwarf a gyroscope of a type that uses light rather than mechanical components. Credit: Pooya Vahidi

Optics and photonics

World’s littlest light-sensing gyroscope fits on a grain of rice

Advanced version of an optical gyroscope cuts noise from scattered light.

Engineers have designed the world’s smallest version of an optical gyroscope, a device that relies on light rather than moving parts, in a feat that could lead to models with much higher precision than comparable mechanical devices.

Inside a conventional optical gyroscope, a spooled-up optical fibre carries pulses of laser light, some running clockwise and some running anticlockwise. The device measures the rate of rotation by detecting tiny shifts in the timing of the pulses’ arrival at a sensor. Optical gyros have been difficult to scale down because, as they shrink, the signal from their sensors weakens and is then drowned in noise created in part by scattered light.

To counteract this effect, Parham Khial and his colleagues at the California Institute of Technology in Pasadena designed a low-noise, photonic gyroscope. The researchers etched light-guiding channels onto a 2-square-millimetre silicon chip to guide the light travelling in each direction around a separate circle, so that scattered light would not confuse the device’s sensors. The new design also periodically reverses the light’s direction, helping to cancel out much of the noise.