Feeds

Caltech shrinks optical accelerometers

A light alternative to tracking mobes

Boost IT visibility and business value

The practical limit to tracking a smartphone-owner’s movements in real time – beneath the resolution of GPS and associated location-tracking technologies – is the sensitivity of the motion sensor. Researchers at Caltech say they’ve taken a step towards very fine motion sensors, using nano-scale waveguides.

Today’s smartphones use electrical accelerometers. While these are already small enough for the application, sensitivity is limited, as researcher Oskar Painter explains.

“Most sensors are completely limited by thermal noise, or mechanical vibrations—they jiggle around at room temperature, and applied accelerations get lost in that noise,” he explains in Caltech’s announcement.

The green proof masses are suspended across

cavities - not visible here - which use lasers

to sense their movement. Scanning electron

microscope image: Martin Winger & Caltech

Instead of an electrical accelerometer (a displacement circuit measuring the movement of a “proof mass”), Painter’s group focussed on miniaturising optical accelerometers, which use reflected light beams to measure the proof mass displacement. While already used in high-sensitivity science applications – like the Laser Interferometry Gravitational-Wave Observatory – such detectors are hardly miniature (the LIGO mirrors are separated by kilometres).

Down at micro-scale, Painter’s group created a proof mass etched into a chip. These are suspended across optical cavities that are 20 microns long and one micron wide, and a few tenths of a micron thick. Two waveguides (“nanobeams”) in the cavity, one of which is attached to the proof mass, direct a laser and detect how its reflections change with movement of the proof mass.

The sensitivity of the detector reaches down to a few femtometers, the researchers say.

Even cooler – forgive the pun – because everything in the system is so small, the lasers damp unwanted movement in the proof mass.

“In our device, the light applies a force that tends to reduce the thermal motion, cooling the system,” Painter said – down to a temperature of three Kelvins (about –270°C) in the current devices.

That gives the detector the flexibility to sense both very large and very small accelerations, making it suitable for oil and gas exploration, bio-medical sensors, and aircraft applications.

Oh, and yes: if commercialised, a nano-scale optical accelerometer would be sensitive enough to map a shopper’s movements within a supermarket, allowing them to be bombarded with aisle-specific advertisements.

Thanks a lot. ®

5 things you didn’t know about cloud backup

More from The Register

next story
Boffins attempt to prove the UNIVERSE IS JUST A HOLOGRAM
Is this the real life? Is this just fantasy?
China building SUPERSONIC SUBMARINE that travels in a BUBBLE
Shanghai to San Fran in two hours would be a trick, though
Our LOHAN spaceplane ballocket Kickstarter climbs through £8000
Through 25 per cent but more is needed: Get your UNIQUE rewards!
LOHAN Kickstarter push breaks TWELVE THOUSAND POUNDS
That's right, folks, you've stumped up OVER 9000 beer tokens - and counting
SpaceX prototype rocket EXPLODES over Texas. 'Tricky' biz, says Elon Musk
No injuries or near injuries. Flight stayed in designated area
Galileo, Galileo! Galileo, Galileo! Galileo fit to go. Magnifico
I'm just a poor boy, nobody loves me. But at least I can find my way with ESA GPS by 2017
Astronomers scramble for obs on new comet
Amateur gets fifth confirmed discovery
prev story

Whitepapers

7 Elements of Radically Simple OS Migration
Avoid the typical headaches of OS migration during your next project by learning about 7 elements of radically simple OS migration.
Implementing global e-invoicing with guaranteed legal certainty
Explaining the role local tax compliance plays in successful supply chain management and e-business and how leading global brands are addressing this.
Why and how to choose the right cloud vendor
The benefits of cloud-based storage in your processes. Eliminate onsite, disk-based backup and archiving in favor of cloud-based data protection.
Boost IT visibility and business value
How building a great service catalog relieves pressure points and demonstrates the value of IT service management.
High Performance for All
While HPC is not new, it has traditionally been seen as a specialist area – is it now geared up to meet more mainstream requirements?