Andrew Yee[_1_]
May 6th 08, 03:00 AM
National Institute of Standards and Technology
Gaithersburg, Maryland
Media Contact:
Laura Ost, (303) 497-4880
May 5, 2008
Record-setting Laser May Aid Searches for Earthlike Planets
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.
Background on frequency combs and NIST's role in their development can be
found at: "Optical Frequency Combs",
http://www.nist.gov/public_affairs/newsfromnist_frequency_combs.htm
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)
IMAGE CAPTION:
[http://patapsco.nist.gov/ImageGallery/details.cfm?imageid=539]
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
Gaithersburg, Maryland
Media Contact:
Laura Ost, (303) 497-4880
May 5, 2008
Record-setting Laser May Aid Searches for Earthlike Planets
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.
Background on frequency combs and NIST's role in their development can be
found at: "Optical Frequency Combs",
http://www.nist.gov/public_affairs/newsfromnist_frequency_combs.htm
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)
IMAGE CAPTION:
[http://patapsco.nist.gov/ImageGallery/details.cfm?imageid=539]
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