Feeds

Caltech shrinks optical accelerometers

A light alternative to tracking mobes

Secure remote control for conventional and virtual desktops

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. ®

Security for virtualized datacentres

More from The Register

next story
MEN: For pity's sake SLEEP with LOTS of WOMEN - and avoid Prostate Cancer
And, um, don't sleep with other men. If that's what worries you
Voyager 1 now EIGHTEEN LIGHT HOURS from home
Almost 20 BEEELION kilometres from Sol
Jim Beam me up, Scotty! WHISKY from SPAAACE returns to Earth
They're insured for $1m, before you thirsty folks make plans
ROGUE SAIL BOAT blocks SPACE STATION PODULE blastoff
Er, we think our ISS launch beats your fishing expedition
Comet Siding Spring revealed as flying molehill
Hiding from this space pimple isn't going to do humanity's reputation any good
BAE points electromagnetic projectile at US Army
Railguns for 'Future fighting vehicle'
OK Google, do I have CANCER?
Company talks up pill that would spot developing tumors
LONG ARM of the SAUR: Brachially gifted dino bone conundrum solved
Deinocheirus mirificus was a bit of a knuckle dragger
prev story

Whitepapers

Why cloud backup?
Combining the latest advancements in disk-based backup with secure, integrated, cloud technologies offer organizations fast and assured recovery of their critical enterprise data.
Forging a new future with identity relationship management
Learn about ForgeRock's next generation IRM platform and how it is designed to empower CEOS's and enterprises to engage with consumers.
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?
New hybrid storage solutions
Tackling data challenges through emerging hybrid storage solutions that enable optimum database performance whilst managing costs and increasingly large data stores.
Getting ahead of the compliance curve
Learn about new services that make it easy to discover and manage certificates across the enterprise and how to get ahead of the compliance curve.