Feeds

Caltech shrinks optical accelerometers

A light alternative to tracking mobes

The smart choice: opportunity from uncertainty

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. ®

Eight steps to building an HP BladeSystem

More from The Register

next story
Malaysian Airlines flight MH17 claimed lives of HIV/AIDS cure scientists
Researchers, advocates, health workers among those on shot-down plane
Mwa-ha-ha-ha! Eccentric billionaire Musk gets his PRIVATE SPACEPORT
In the Lone Star State, perhaps appropriately enough
The Sun took a day off last week and made NO sunspots
Someone needs to get that lazy star cooking again before things get cold around here
All those new '5G standards'? Here's the science they rely on
Radio professor tells us how wireless will get faster in the real world
Diary note: Pluto's close-up is a year from … now!
New Horizons is less than a year from the dwarf planet
Boffins discuss AI space program at hush-hush IARPA confab
IBM, MIT, plenty of others invited to fill Uncle Sam's spy toolchest, but where's Google?
prev story

Whitepapers

Seven Steps to Software Security
Seven practical steps you can begin to take today to secure your applications and prevent the damages a successful cyber-attack can cause.
Consolidation: The Foundation for IT Business Transformation
In this whitepaper learn how effective consolidation of IT and business resources can enable multiple, meaningful business benefits.
Designing a Defense for Mobile Applications
Learn about the various considerations for defending mobile applications - from the application architecture itself to the myriad testing technologies.
Build a business case: developing custom apps
Learn how to maximize the value of custom applications by accelerating and simplifying their development.
Consolidation: the foundation for IT and business transformation
In this whitepaper learn how effective consolidation of IT and business resources can enable multiple, meaningful business benefits.