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Quantum Noise Reduction in Lasers Through Nonlinear Intracavity Dynamics

  • H. Ritsch
  • P. Zoller
Chapter

Abstract

As can be found in almost any textbook on laser physics, standard theories for a single mode laser predict, that far above threshold the laser generates nearly a coherent state (with a phase randomly varying in time). Hence the counting statistics for the output photons is Poissonian and the intensity fluctuation spectrum is shot noise limited (this defines the so-called standard quantum limit (SQL)). A closer investigation reveals three main sources of the laser quantum intensity fluctuations, namely pump noise, noise through cavity losses and spontaneous emission noise. The last contribution, which turns out to be less important far above threshold, can be minimized by proper choice of the laser transition. Recently there has been increased interest in developing a so called quiet laser, i.e. a laser with sub-shotnoise intensity fluctuations. In this context several authors have proposed a laser with an external sub-Poissonian pump 1-6 (i.e. pumping with amplitude squeezed light or a sequence of regularly spaced short pump pulses, as well as injection of a regular beam of excited atoms, electrons), which leads to an intensity noise reduction below the standard quantum limit. In the best case the variance of the laser photon number distribution is reduced by a factor of 2 compared to the Poissonian case and the slow output intensity fluctuations around zero frequency are completely suppressed. In contrast to an external sub-Poissonian pump, in this work we will present two alternative mechanisms to quench the quantum noise in a laser, which do not rely on some externally injected regularity, but are based on nonlinear dynamic self regularization.7-11

Keywords

Coherent State Noise Reduction Photon Number Lasing Level Nonlinear Feedback 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Plenum Press, New York 1993

Authors and Affiliations

  • H. Ritsch
    • 1
  • P. Zoller
    • 2
  1. 1.Institute for Theoretical PhysicsUniversity of InnsbruckInnsbruckAustria
  2. 2.Joint Institute for Laboratory Astrophysics & Dept.of PhysicsUniversity of ColoradoBoulderUSA

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