Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Active optical clock

15.04.2009
Institute of Quantum Electronics, School of Electronics Engineering and Computer Science, Peking University, has proposed the concept, principles and techniques of active optical clock. The study is reported in Issue 54 (February, 2009) of Chinese Science Bulletin because of its significant research value.

Up to date, all realize that optical clocks are based on the laser absorption spectroscopy. Thus the available laser with narrowest linewidth limits the linewidth of state-of-the-art optical clocks. However, experimental and theoretical results show that the thermal Johnson noise of cavity mirrors degrades the quantum limitation of Schawlow-Townes linewidth formula of good-cavity laser.

In this work, Prof. Chen proposed the concept, principles and techniques of active optical clock. This is the first extension of Hydrogen maser, which is the most stable atomic microwave clock and related to the Nobel Prize in Physics 1989, from microwave regime to optical regime.

The lasing behavior of active optical clock is a second-order phase transition. On the one hand, the collective emission of radiation from all gain atoms strongly narrows the linewidth of active optical clock described by the modified Schawlow-Townes linewidth formula. On the other hand, in an active optical clock, any shift and noise of the center frequency due to cavity will be reduced to a cavity pulling effect, which can be several orders of magnitude smaller than the general cavity noise.

"Active optical clocks provide several new possibilities of applications: (i) more stable optical clock than any current atomic clocks; (ii) sub-natural linewidth laser spectroscopy; (iii) long coherence time laser with linewidth at mHz level; (iv) Ramsey laser combining stimulated emission process and Ramsey separated oscillatory fields method." commented Prof. Yiqiu Wang, the co-author of the first book "The principles of quantum frequency standards" in the research field of quantum frequency standards. A series of papers about active optical clock written by Prof. Chen and colleagues have been published in Chin. Sci. Bull., Phys. Rev. A, etc. "It is a novel idea. The active optical clock enriched and expanded the optical clock research." said one reviewer.

The author is affiliated at Institute of Quantum Electronics of Peking University. This institute has been conducting research in a variety of atomic clocks for four decades.

Supported by the National Natural Science Foundation of China (Grant Nos. 10874009) and the National Basic Research Program of China (Grant No. 2005CB724500).

Reference:

Chen J. Active optical clock. Chin Sci Bull. 2009; 54(3): 348-352 http://219.238.6.200/article?code=982008-2451&jccode=98

Wang Y Q. Optical clock based on stimulated emission radiation. Chin Sci Bull. 2009; 54(3): 347-347 http://219.238.6.200/article?code=982008-2580&jccode=98

Yu D and Chen J. Laser theory with finite atom-field interacting time. Phys. Rev. A 2008; 78, 013846-1-013846-8 http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=PLRAAN000078000001013846000001&idtype=cvips&gifs=yes

J Chen | EurekAlert!
Further information:
http://www.pku.edu.cn

More articles from Physics and Astronomy:

nachricht Engineering team images tiny quasicrystals as they form
18.08.2017 | Cornell University

nachricht Astrophysicists explain the mysterious behavior of cosmic rays
18.08.2017 | Moscow Institute of Physics and Technology

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: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

A Map of the Cell’s Power Station

18.08.2017 | Life Sciences

Engineering team images tiny quasicrystals as they form

18.08.2017 | Physics and Astronomy

Researchers printed graphene-like materials with inkjet

18.08.2017 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>