Physicists measure 'long' distances with picometer accuracy

December 2, 2005
This NIST vacuum chamber is used to measure millimeter distances more accurately than ever before

A new laser-based method for measuring millimeter distances more accurately than ever before--with an uncertainty of 10 picometers (trillionths of a meter)--has been developed and demonstrated by a physicist at the National Institute of Standards and Technology. This is akin to measuring the distance from New York to Los Angeles with an uncertainty of just 1 millimeter. The technique may have applications in nanotechnology, remote sensing and industries such as semiconductor fabrication.

Image: This NIST vacuum chamber is used to measure millimeter distances more accurately than ever before. Laser light is sent into the chamber through an optical fiber and stored between two highly reflective mirrors (left and bottom arrows), which form an optical cavity. By measuring the frequency of the light, which is tuned to match specific properties of the cavity, a scientist can determine changes in the lower mirror's position with picometer accuracy. Image credit: J. Lawall/NIST

Laser light is typically used to measure distances by counting the number of wavelengths (the distance between successive peaks of the wave pattern) of light between two points. Because the wavelength is very short (633 nanometers for the red light most often used), the method is intrinsically very precise.

Modern problems in nanotechnology and device fabrication, however, require uncertainty far below 633 nm.

A more precise method, described in the December issue of the Journal of the Optical Society of America A, involves measuring the frequency of laser light rather than the wavelength. The laser light is stored between two highly reflective mirrors, to create the optical analog of an organ pipe. The length of an organ pipe can be measured by driving the pipe with sound waves of a known frequency (pitch). The sound emitted by the pipe is loudest when it is driven at one of its "natural" frequencies, commonly called harmonics. When one or more of these frequencies is identified, the pipe length can be determined. In the NIST work, light is transmitted through both mirrors only when the frequency of the light matches a harmonic frequency. This frequency can be used to determine the distance between the mirrors.

While this approach has been used previously for the measurement of short distances (of the order of 1 micrometer), the new work extends it 25,000-fold by demonstrating a range of 25 millimeters. (Ultimately, the design should accommodate a range of up to 50 mm.) In addition, the NIST approach described in the paper excites two harmonics of the optical system, rather than one, a redundancy that increases the range while achieving picometer accuracy.

Publication: J.R. Lawall. 2005. Fabry-Perot metrology for displacements up to 50 mm. Journal of the Optical Society of America A. December 2005.

Source: NIST


Rank 4 /5 (11 votes)
Tags

Relevant PhysicsForums posts

More news stories

Putting the squeeze on planets outside our solar system

(PhysOrg.com) -- Using high-powered lasers, scientists at Lawrence Livermore National Laboratory and collaborators discovered that molten magnesium silicate undergoes a phase change in the liquid state, abruptly ...

Physics / Condensed Matter

created 9 hours ago | popularity 4.4 / 5 (5) | comments 0 | with audio podcast

Hovering not hard if you're top-heavy, researchers find

Top-heavy structures are more likely to maintain their balance while hovering in the air than are those that bear a lower center of gravity, researchers at New York University's Courant Institute of Mathematical Sciences ...

Physics / General Physics

created 10 hours ago | popularity 5 / 5 (1) | comments 1 | with audio podcast

SLAC, Stanford team focuses on high-energy electrons to treat cancer

Accelerator physicists at SLAC and cancer specialists from Stanford are working on a new technology that could dramatically reduce the time needed for cancer radiation treatments. The team ran an initial experiment ...

Physics / General Physics

created 13 hours ago | popularity 5 / 5 (1) | comments 0

Measurements from high-energy collisions lead to better understanding of why meson particles disappear

For several years, physicists at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL), USA, have studied an unusual state of matter called the quark–gluon plasma, which they ...

Physics / General Physics

created 13 hours ago | popularity 4.5 / 5 (2) | comments 0

Explained: Sigma

It's a question that arises with virtually every major new finding in science or medicine: What makes a result reliable enough to be taken seriously? The answer has to do with statistical significance -- but ...

Physics / General Physics

created Feb 09, 2012 | popularity 5 / 5 (16) | comments 53


Google users warned of threat to smartphone wallets

Users of Google smartphone wallets were being warned on Friday that there is a way to crack pass codes intended to thwart thieves from going on illicit shopping sprees.

Anonymous knocks CIA website offline (Update)

The website of the Central Intelligence Agency was inaccessible on Friday after the hacker group Anonymous claimed to have knocked it offline.

New error-correcting codes guarantee the fastest possible rate of data transmission

Error-correcting codes are one of the triumphs of the digital age. They’re a way of encoding information so that it can be transmitted across a communication channel — such as an optical fiber o ...

Complex wiring of the nervous system may rely on a just a handful of genes and proteins

Researchers at the Salk Institute have discovered a startling feature of early brain development that helps to explain how complex neuron wiring patterns are programmed using just a handful of critical genes. ...

The power of estrogen -- male snakes attract other males

A new study has shown that boosting the estrogen levels of male garter snakes causes them to secrete the same pheromones that females use to attract suitors, and turned the males into just about the sexiest ...

Humans may have helped the decline of African rainforests 3000 years ago

(PhysOrg.com) -- Large areas of rainforests in Central Africa mysteriously disappeared over three thousand years ago, to be replaced by savannas. The prevailing theory has been that the cause was a change ...