Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Nobel Prize Technique on a Chip

20.12.2007
The frequency comb technique invented at the Max Planck Institute of Quantum Optics (MPQ) in Garching, Germany, has influenced and advanced basic research as well as laser development and its applications to such an extent that in 2005 its inventor Theodor Hänsch (MPQ) was awarded the Nobel Prize in Physics together with his US-colleague John Hall.

The high-precision measuring instruments for determining optical frequencies have meanwhile been made relatively compact and become commercially available. Much handier, however, is the just 75 micrometres in diameter microresonator with which Dr. Tobias Kippenberg and co-workers from the 'Laboratory of Photonics' at MPQ succeeded in generating frequency combs (Nature, 20 December 2007). Frequency combs on a microchip could revolutionize time measurement and data transmission techniques.


Light of one single frequency, symbolized by the green line on the left side, is converted to a frequency comb within the microresonator, pictured by a bunch of coloured lines on the right side of the image. MPQ

A frequency comb is in principle a kind of 'ruler' with which unknown optical, i.e. very high, frequencies of light can be determined with extremely high precision. The concept investigated by Hänsch and Hall is based on a mode-coupling process in short-pulse lasers. This produces laser light containing about 100,000 closely spaced spectral lines whose frequency distance is always equal and known with extreme exactness - hence the designation 'comb'. The superposition of this comb with another laser beam results in a pattern from which the unknown laser frequency can be determined with hitherto unattained accuracy. This conventional set-up of a frequency comb consists of very many optical components and is therefore very bulky.

The independent Max Planck junior research group of Dr. Tobias Kippenberg - since 2007 also funded by a "Marie Curie Excellence Grant" - has now in cooperation with Ronald Holzwarth from Menlo Systems (this offshoot company established by MPQ is meanwhile marketing the frequency comb technology worldwide) succeeded in generating a frequency comb by means of a tiny microstructure. In their experiment the scientists use a toroidal glass resonator with a diameter of just 75 micrometres that is produced on a silicon chip at the Chair of Solid State Physics (Prof. Jörg Kotthaus) of Ludwig Maximilian's University (LMU), Munich. By passing a laser beam in a "nanowire" made of glass close to it they couple light into this monolithic structure.
Such optical resonators can store light for a relatively long period. This can lead to extremely high light intensities, i.e. photon densities, at which a great deal of nonlinear effects occur. And it is such a nonlinear 'Kerr effect' that makes it possible to realise a frequency comb: In a 4-photon process two light quanta of equal energies are converted to two photons of which the one light quantum has a higher energy, the other a lower energy than the original one. Here the newly produced photons can in turn interact with the original light quanta, thereby producing new frequencies. From this cascade there emerges a surprisingly broad spectrum of frequencies without any resort to amplification by an active laser medium, as is necessary in the conventional method. "It is noteworthy that there had been no mention in the literature that frequency combs could be generated in this way", states Pascal Del'Haye, a Ph.D. student at the project. "What we have here is a completely new and surprisingly efficient generation process", confirms Dr. Tobias Kippenberg.

The new method, however, is only suitable if the distances between all of the frequencies produced are always exactly equal and in this way yield a perfect comb - although the microresonators themselves do not have a perfectly equidistant mode spectrum. In high precision measurements Ph.D. students Pascal Del'Haye and Albert Schließer compared the spectrum of the monolithically generated frequency comb with a commercial version provided by the Menlo Systems company. They showed that the frequencies produced in the microresonator are equidistant, and were able to rule out deviations of as small as 10-18 of the light frequencies.

This new type of frequency comb could be used in the future for optical frequency measurements and also for designing clocks of extremely high precision. Another highly interesting field of application is in optical telecommunications: Whereas in the conventional frequency comb the lines are extremely close and of very low intensity, the approximately 130 spectral lines of the monolithic frequency comb have a separation of about 400 gigahertz and powers of the order of one milliwatt (0 dBm). This spacing and power level corresponds to the typical requirements for the "carriers" of the data channels in fibre-based optical communications. Whereas every frequency channel has hitherto needed its own generator with its own laser, the novel device would make it possible to define a large number of data channels with one single monolithic microcavity.

Not all aspects of the process have as yet been clarified, and the technique has still to be elaborated before the frequency comb can be put into practical application. In view of its high application potential the scientists have nevertheless already applied for patents worldwide.

The work recently presented in Nature was conducted in the context of the "Nanosystems Initiative Munich" cluster of excellence, whose objective is to develop, research and apply functional nanostructures in medicine and information processing. [O.M.]

Publication:
"Optical frequency comb generation from a monolithic microresonator",
P. Del'Haye, A. Schliesser, O. Arcizet, T. Wilken, R. Holzwarth, T. J. Kippenberg, Nature, 20 December 2007
Contact:
Dr. Tobias Kippenberg
Max Planck Institute of Quantum Optics
Hans-Kopfermann-Straße 1
85748 Garching
Phone: +49 - 89 / 32905 727
Fax: +49 - 89 / 32905 200
E-mail: tobias.kippenberg@mpq.mpg.de
Dr. Olivia Meyer-Streng
Press & Public Relations
Max Planck Institute of Quantum Optics
Hans-Kopfermann-Straße 1
85748 Garching
Phone: +49 - 89 / 32905 213
Fax: +49 - 89 / 32905 200
E-mail: olivia.meyer-streng@mpq.mpg.de

Dr. Olivia Meyer-Streng | Max-Planck-Gesellschaft
Further information:
http://www.mpq.mpg.de/k-lab/

More articles from Physics and Astronomy:

nachricht Explosion on Jupiter-sized star 10 times more powerful than ever seen on our sun
18.04.2019 | University of Warwick

nachricht In vivo super-resolution photoacoustic computed tomography by localization of single dyed droplets
18.04.2019 | Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Explosion on Jupiter-sized star 10 times more powerful than ever seen on our sun

A stellar flare 10 times more powerful than anything seen on our sun has burst from an ultracool star almost the same size as Jupiter

  • Coolest and smallest star to produce a superflare found
  • Star is a tenth of the radius of our Sun
  • Researchers led by University of Warwick could only see...

Im Focus: Quantum simulation more stable than expected

A localization phenomenon boosts the accuracy of solving quantum many-body problems with quantum computers which are otherwise challenging for conventional computers. This brings such digital quantum simulation within reach on quantum devices available today.

Quantum computers promise to solve certain computational problems exponentially faster than any classical machine. “A particularly promising application is the...

Im Focus: Largest, fastest array of microscopic 'traffic cops' for optical communications

The technology could revolutionize how information travels through data centers and artificial intelligence networks

Engineers at the University of California, Berkeley have built a new photonic switch that can control the direction of light passing through optical fibers...

Im Focus: A long-distance relationship in femtoseconds

Physicists observe how electron-hole pairs drift apart at ultrafast speed, but still remain strongly bound.

Modern electronics relies on ultrafast charge motion on ever shorter length scales. Physicists from Regensburg and Gothenburg have now succeeded in resolving a...

Im Focus: Researchers 3D print metamaterials with novel optical properties

Engineers create novel optical devices, including a moth eye-inspired omnidirectional microwave antenna

A team of engineers at Tufts University has developed a series of 3D printed metamaterials with unique microwave or optical properties that go beyond what is...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Revered mathematicians and computer scientists converge with 200 young researchers in Heidelberg!

17.04.2019 | Event News

First dust conference in the Central Asian part of the earth’s dust belt

15.04.2019 | Event News

Fraunhofer FHR at the IEEE Radar Conference 2019 in Boston, USA

09.04.2019 | Event News

 
Latest News

New automated biological-sample analysis systems to accelerate disease detection

18.04.2019 | Life Sciences

Explosion on Jupiter-sized star 10 times more powerful than ever seen on our sun

18.04.2019 | Physics and Astronomy

New eDNA technology used to quickly assess coral reefs

18.04.2019 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>