Record-setting Laser May Aid Searches for Earthlike Planets

May 05, 2008
Record-setting Laser May Aid Searches for Earthlike Planets
Experimental data from a NIST "gap-toothed" frequency comb that are false colored to indicate the range from low power (red) to high power (blue). The comb is specially designed for astronomy. Each "tooth" is a precisely known frequency, and the teeth are widely separated (by 20 gigahertz) in comparison to a standard comb. Credit: M. Kirchner & S. Diddams/NIST

Scientists at the University of Konstanz in Germany and the National Institute of Standards and Technology (NIST) have demonstrated an ultrafast laser that offers a record combination of high speed, short pulses and high average power. The same NIST group also has shown that this type of laser, when used as a frequency comb—an ultraprecise technique for measuring different colors of light—could boost the sensitivity of astronomical tools searching for other Earthlike planets as much as 100 fold.

The dime-sized laser, to be described Thursday, May 8, at the Conference on Lasers and Electro-Optics,* emits 10 billion pulses per second, each lasting about 40 femtoseconds (quadrillionths of a second), with an average power of 650 milliwatts. For comparison, the new laser produces pulses 10 times more often than a standard NIST frequency comb while producing much shorter pulses than other lasers operating at comparable speeds. The new laser is also 100 to 1000 times more powerful than typical high-speed lasers, producing clearer signals in experiments. The laser was built by Albrecht Bartels at the Center for Applied Photonics of the University of Konstanz.

Among its applications, the new laser can be used in searches for planets orbiting distant stars. Astronomers look for slight variations in the colors of starlight over time as clues to the presence of a planet orbiting the star. The variations are due to the small wobbles induced in the star’s motion as the orbiting planet tugs it back and forth, producing minute shifts in the apparent color (frequency) of the starlight. Currently, astronomers’ instruments are calibrated with frequency standards that are limited in spectral coverage and stability.

Frequency combs could be more accurate calibration tools, helping to pinpoint even smaller variations in starlight caused by tiny Earthlike planets. Such small planets would cause color shifts equivalent to a star wobble of just a few centimeters per second. Current instruments can detect, at best, a wobble of about 1 meter per second.

Standard frequency combs have “teeth” that are too finely spaced for astronomical instruments to read. The faster laser is one approach to solving this problem. In a separate paper,** the NIST group and astronomer Steve Osterman at the University of Colorado at Boulder describe how, by bouncing the light between sets of mirrors a particular distance apart, they can eliminate periodic blocks of teeth to create a gap-toothed comb. This leaves only every 10th or 20th tooth, making an ideal ruler for astronomy.

Both approaches have advantages for astronomical planet finding and related applications. The dime-sized laser is very simple in construction and produces powerful and extremely well-defined comb teeth. On the other hand, the filtering approach can cover a broader range of wavelengths. Four or five filtering cavities in parallel would provide a high-precision comb of about 25,000 evenly spaced teeth that spans the visible to near-infrared wavelengths (400 to 1100 nanometers), NIST physicist Scott Diddams says.

Osterman says he is pursuing the possibility of testing such a frequency comb at a ground-based telescope or launching a comb on a satellite or other space mission. Other possible applications of the new laser include remote sensing of gases for medical or atmospheric studies, and on-the-fly precision control of high-speed optical communications to provide greater versatility in data and time transmissions. The application of frequency combs to planet searches is of international interest and involves a number of major institutions such as the Max-Planck Institute for Quantum Optics and Harvard Smithsonian Center for Astrophysics.

References:

* A. Bartels, D. Heinecke and S.A. Diddams. Passively mode-locked 10 GHz femtosecond Ti:sapphire laser with >1 mW of power per frequency comb mode. Post-deadline paper presented at Conference on Lasers and Electro-Optics (CLEO), San Jose, Calif., May 4-9, 2008.

** D.A. Braje, M. S. Kirchner, S. Osterman, T. Fortier and S. A. Diddams. Astronomical spectrograph calibration with broad-spectrum frequency combs. To appear in European Physics Journal D. (Posted online at arXiv:0803.0565)

Source: NIST

Explore further: New terahertz device could strengthen security

add to favorites email to friend print save as pdf

Related Stories

NIST 'combs' the atmosphere to measure greenhouse gases

Oct 29, 2014

By remotely "combing" the atmosphere with a custom laser-based instrument, researchers from the National Institute of Standards and Technology (NIST), in collaboration with researchers from the National Oceanic ...

Recommended for you

New terahertz device could strengthen security

21 hours ago

We are all familiar with the hassles that accompany air travel. We shuffle through long lines, remove our shoes, and carry liquids in regulation-sized tubes. And even after all the effort, we still wonder if these procedures ...

CERN makes public first data of LHC experiments

Nov 21, 2014

CERN today launched its Open Data Portal where data from real collision events, produced by experiments at the Large Hadron Collider (LHC) will for the first time be made openly available to all. It is expected ...

New technique allows ultrasound to penetrate bone, metal

Nov 20, 2014

Researchers from North Carolina State University have developed a technique that allows ultrasound to penetrate bone or metal, using customized structures that offset the distortion usually caused by these ...

User comments : 2

Adjust slider to filter visible comments by rank

Display comments: newest first

okazakifudosan
1 / 5 (5) May 05, 2008
%u305D%u308C%u306B%u3057%u3066%u3082%u4E88%u6E2C%u4E0D%u53EF%u80FD%u306A%u7BC4%u56F2%u3067%u30AB%u30BF%u30AB%u30CA%u306B%u5909%u63DB%u3055%u308C%u308B%u30A6%u30C1%u306EIME%u306F%u3069%u3046%u306B%u304B%u306A%u3089%u3093%u306E%u3067%u3057%u3087%u3046%u304B
%u51FA%u4F1A%u3044%u7CFB%u3000%u767B%u9332
EarthScientist
1 / 5 (1) May 06, 2008
I see okookie before me has it figured,but I figure it a little different,Most quadrants have 2 planets that are habitable,Mars is our other habitable planet,but its grid is shut down to 30 percent total heating due to the 14 thousand ago problem with destruction from the explosion components from the 28 ago planetary explosion.Its amazing that folks have to spend billions to try and find out all of the "secrets" of the universe when the grid men and lifter men can just give it to you ,nice and easy,plain and simple if you can handle it.Come get me ,NSA.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.