Berlin 2001 – scientific programme

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AMPD: EPS AMPD

AMPD 7: Sitzung 7

AMPD 7.3: Talk

Thursday, April 5, 2001, 11:30–11:55, H105

Quantum noise reduction in Optical Parametric Oscillators — •T. Coudreau, K.S. Zhang, M. Martinelli, L. Longchambon, N. Treps, S. Ducci, A. Maître, and C. Fabre — Laboratoire Kastler Brossel, ENS, CNRS et Université Pierre et Marie Curie, Case 74, U.P.M.C., 4, Place Jussieu 75252 Paris cedex 05, France

Optical Parametric Oscillators (OPOs) produce coherent and tunable light beams with a good efficiency. They are now widely used, mainly in pulsed operation, for example for spectroscopic applications. But they turn out to be also very efficient sources of light having pure quantum features: squeezed light, twin beams, quantum non demolition measurement devices...

The first part of my talk will be devoted to some new advances in the classical properties of OPOs, namely, the introduction of quasi-phase matched materials and the development of phase–locked OPOs.

The introduction of quasi–phase matched materials has opened a whole new wavelength range for the generation of coherent light allowing single sources to generate light continuously tunable over large regions in the mid–infrared. We have in particular obtained c.w. OPOs with an oscillation threshold below 1 mW when pumped by an Nd:YAG laser and generating signal and idler close to 2 µ m.

The insertion of a birefringent plate inside the OPO induces a coupling between signal and idler which in some cases makes it possible to obtain phase–locking between the two beams and as a consequence exact frequency degenerate operation. This makes it possible in particular to obtain a perfect frequency divider.

The second part of my talk will describe recent development in the quantum features of OPOs.

I will show how the use of quasi–phase matched materials makes it possible to obtain an efficient "quantum noise eater". This device is able to reduce the fluctuations of a beam in the near infrared and with powers in the mW below the standard quantum limit.

I will also describe how a phase–locked OPO can be used as an efficient source for entangled beams. OPOs have been known for a long time to be able to generate beams with large intensity correlations. Phase–locked OPOs should also present large phase anticorrelations between signal and idler. This makes the OPO a very promising source for the generation of EPR type beams to be used in quantum teleportation or quantum cryptography experiments with continuous variables.