Letter abstract

Nature Physics 6, 350 - 353 (2010)
Published online: 28 March 2010 | doi:10.1038/nphys1627

Subject Categories: Atomic and molecular physics | Optical physics | Quantum physics

Quantum to classical transition in a single-ion laser

François Dubin1,2, Carlos Russo1,4, Helena G. Barros1,3, Andreas Stute1,3, Christoph Becher1,4, Piet O. Schmidt1,4 & Rainer Blatt1,3


The onset of lasing in a ‘classical’ laser1 is marked by a threshold that can be characterized by a sharp increase in photon flux as a function of external pumping strength2, 3. The same is not necessarily true for a single trapped atom interacting with a single optical mode4, 5, 6. ‘Quantum’ lasers have shown thresholdless lasing in the regime of strong coupling between an atom and a radiation field7, 8, but the existence of a threshold has been predicted9, 10, 11, 12. Here, we demonstrate and characterize a single-atom laser with and without threshold behaviour by changing the strength of atom/light-field coupling. We observe the establishment of a laser threshold through the accumulation of photons in the optical mode even for a mean photon number substantially lower than for the classical case. Our observations mark an important step towards a fundamental understanding of laser operation in the few-atom limit13 including systems based on semiconductor quantum dots14 or molecules15.

  1. Institut für Experimentalphysik, Universität Innsbruck, Technikerstr. 25, 6020 Innsbruck, Austria
  2. ICFO-Institut de Ciències Fotòniques, Mediterranean Technology Park, 08860 Castelldefels, Spain
  3. Institut für Quantenoptik und Quanteninformation, Österreichische Akademie der Wissenschaften, Otto-Hittmair-Platz 1, 6020 Innsbruck, Austria
  4. Present addresses: GoLP/Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Av., Rovisco Pais, 1049-001 Lisboa, Portugal (C.R.); Fachrichtung Technische Physik, Universität des Saarlandes, Campus E2.6, 66123 Saarbrücken, Germany (C.B.); QUEST Institut für Experimentelle Quantenmetrologie, Physikalisch-Technische Bundesanstalt und Leibniz Universität Hannover, Bundesallee 100, 38116 Braunschweig, Germany (P.O.S.)

Correspondence to: Piet O. Schmidt1,4 e-mail: Piet.Schmidt@ptb.de


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