T. Legero

Publications (10)11.46 Total impact

• Source

  Available from: Markus Hennrich

  Article: Photon statistics of a non-stationary periodically driven single-photon source

  M Hennrich, T Legero, A Kuhn, G Rempe
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  ABSTRACT: We investigate the photon statistics of a single-photon source that operates under non-stationary conditions. The photons are emitted by shining a periodic sequence of laser pulses on single atoms falling randomly through a high-finesse optical cavity. Strong antibunching is found in the intensity correlation of the emitted light, demonstrating that a single atom emits photons one at a time. However, the number of atoms interacting with the cavity follows a Poissonian statistics so that, on average, no sub-Poissonian photon statistics is obtained, unless the measurement is conditioned on the presence of single atoms.
  New Journal of Physics 11/2012; 6:86. · 4.18 Impact Factor
• Source

  Available from: arxiv.org

  Article: Demonstration of a transportable 1 Hz-linewidth laser

  S. Vogt, C. Lisdat, T. Legero, U. Sterr, I. Ernsting, A. Nevsky, S. Schiller
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  ABSTRACT: We present the setup and test of a transportable clock laser at 698nm for a strontium lattice clock. Amaster-slave diode laser system is stabilized to a rigidly mounted optical reference cavity. The setup was transported by truck over 400km from Braunschweig to Düsseldorf, where the cavity-stabilized laser was compared to a stationary clock laser for the interrogation of ytterbium (578nm). Only minor realignments were necessary after the transport. The lasers were compared using a Ti:Sapphire frequency comb as a transfer oscillator. The generated virtual beat showed a combined linewidth below 1Hz (at 1156nm). The transport back to Braunschweig did not degrade the laser performance, as was shown by interrogating the strontium clock transition.
  Applied Physics B 04/2012; 104(4):741-745. · 2.19 Impact Factor
• Article: Phase-coherent comparison of two optical frequency standards over 146 km using a telecommunication fiber link

  O. Terra, G. Grosche, K. Predehl, R. Holzwarth, T. Legero, U. Sterr, B. Lipphardt, H. Schnatz
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  ABSTRACT: We have explored the performance of two “dark fibers” of a commercial telecommunication fiber link for a remote comparison of optical clocks. The two fibers, linking the Leibniz University of Hanover (LUH) with the Physikalisch-Technische Bundesanstalt (PTB) in Braunschweig, are connected in Hanover to form a total fiber length of 146 km. At PTB the performance of an optical frequency standard operating at 456 THz was imprinted to a cw transfer laser at 194 THz, and its frequency was transmitted over the fiber. In order to detect and compensate phase noise related to the optical fiber link we have built a low-noise optical fiber interferometer and investigated noise sources that affect the overall performance of the optical link. The frequency stability at the remote end has been measured using the clock laser of PTB’s Yb+ frequency standard operating at 344 THz. We show that the frequency of a frequency-stabilized fiber laser can be transmitted over a total fiber length of 146km with a relative frequency uncertainty below 1×10−19, and short term frequency instability given by the fractional Allan deviation of σ y (τ)=3.3×10−15/(τ/s).
  Applied Physics B 04/2012; 97(3):541-551. · 2.19 Impact Factor
• Article: Phase-coherent frequency comparison of optical clocks using a telecommunication fiber link

  H. Schnatz, O. Terra, K. Predehl, T. Feldmann, T. Legero, B. Lipphardt, U. Sterr, G. Grosche, R. Holzwarth, T.W. Hansch, T. Udem, Z.H. Lu, L.J. Wang, W. Ertmer, J. Friebe, A. Pape, E.-M. Rasel, M. Riedmann, T. Wubbena
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  ABSTRACT: We have explored the performance of 2 "dark fibers" of a commercial telecommunication fiber link for a remote comparison of optical clocks. These fibers establish a network in Germany that will eventually link optical frequency standards at PTB with those at the Institute of Quantum Optics (IQ) at the Leibniz University of Hanover, and the Max Planck Institutes in Erlangen (MPL) and Garching (MPQ). We demonstrate for the first time that within several minutes a phase coherent comparison of clock lasers at the few 10^-15 level can also be accomplished when the lasers are more than 100 km apart. Based on the performance of the fiber link to the IQ, we estimate the expected stability for the link from PTB to MPQ via MPL that bridges a distance of approximately 900 km.
  IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control 02/2010; · 1.69 Impact Factor
• Article: Interrogation Laser for a Strontium Lattice Clock

  T. Legero, C. Lisdat, J.S.R. Vellore Winfred, H. Schnatz, G. Grosche, F. Riehle, U. Sterr
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  ABSTRACT: We report on the setup and characterization of a 698-nm master-slave diode laser system to probe the ¹S₀-³P₀ clock transition of strontium atoms confined in a 1-D optical lattice. A linewidth on the order of about 100 Hz of the laser system has been measured with respect to an ultrastable 657-nm diode laser with 1-Hz linewidth using a femtosecond fiber comb as a transfer oscillator. The laser has been used to measure the magnetically induced ¹S₀-³P₀ clock transition in ⁸⁸Sr, where a linewidth of 165 Hz has been observed. The transfer oscillator method provides a virtual beat signal between the two diode lasers that has been used to phase lock the 698-nm laser to the 1-Hz-linewidth laser at 657 nm, transferring its stability to the 698-nm laser system.
  IEEE Transactions on Instrumentation and Measurement 05/2009; · 1.21 Impact Factor
• Conference Proceeding: Clock laser system for strontium lattice clock

  T. Legero, C. Lisdat, J.S.R.V. Winfred, H. Schnatz, G. Grosche, F. Riehle, U. Sterr
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  ABSTRACT: We report on the setup and characterization of a 698 nm master-slave diode laser system to probe the ¹S₀-³P₀ clock transition of strontium atoms confined in a 1D optical lattice. The instability and the line-width of the laser system have been measured with respect to an ultrastable 657 nm diode laser with 1 Hz linewidth utilizing the transfer oscillator principle with a femtosecond fiber comb. The magnetic-field-induced clock transition of ⁸⁸Sr can be used to investigate the instability of the 698 nm clock laser system at intermediate averaging times .
  Precision Electromagnetic Measurements Digest, 2008. CPEM 2008. Conference on; 07/2008
• Source

  Available from: articles.adsabs.harvard.edu

  Article: Neutral Atom Optical Frequency Standards at PTB

  F. Riehle, T. Nazarova, H. Schnatz, T. Legero, U. Sterr
  05/2006; 621:115.
• Source

  Available from: arxiv.org

  Article: Characterization of single photons using two-photon interference

  T. Legero, T. Wilk, A. Kuhn, G. Rempe
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  ABSTRACT: Adiabatic passage techniques allow the generation of single photons which are very long compared to the typical detector time resolution. Therefore the detection time of a photon can be measured within the duration of the single-photon wavepacket. As a consequence, two-photon interference can be investigated in a time-resolved manner, i.e., the coincidence rate can be measured as a function of the time between photodetections. The theoretical analysis shows that this method not only gives information about the duration of single photons, but also about their coherence time. Here we discuss how to use this method for a spectral or temporal characterization of a single-photon source.
  12/2005;
• Source

  Available from: arxiv.org

  Article: Time-Resolved Two-Photon Quantum Interference

  T. Legero, T. Wilk, A. Kuhn, G. Rempe
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  ABSTRACT: The interference of two independent single-photon pulses impinging on a beam splitter is analysed in a generalised time-resolved manner. Different aspects of the phenomenon are elaborated using different representations of the single-photon wave packets, like the decomposition into single-frequency field modes or spatio-temporal modes matching the photonic wave packets. Both representations lead to equivalent results, and a photon-by-photon analysis reveals that the quantum-mechanical two-photon interference can be interpreted as a classical one-photon interference once a first photon is detected. A novel time-dependent quantum-beat effect is predicted if the interfering photons have different frequencies. The calculation also reveals that full two-photon fringe visibility can be achieved under almost any circumstances by applying a temporal filter to the signal. Comment: 6 pages, 4 figures
  08/2003;
• Article: Single atoms and single photons in cavity quantum electrodynamics

  G. Rempe, T. Fischer, M. Hennrich, A. Kuhn, T. Legero, P. Maunz, P. W. H. Pinkse, T. Puppe
  Coherence and Quantum Optics VIII, 241-248 (2003).