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Q: Fachverband Quantenoptik und Photonik

Q 28: Quanteninformation: Photonen III

Q 28.4: Talk

Tuesday, March 3, 2009, 17:15–17:30, VMP 6 HS-D

Mode mapping in waveguided parametric downconversion — •Andreas Christ, Kaisa Laiho, Andreas Eckstein, and Christine Silberhorn — Max Planck Research Group, Günther-Scharowsky-Str. 1/Bau 24, 91058 Erlangen, Germany

The process of parametric downconversion (PDC) has been found a reliable source of entangled photon pairs for quantum cryptography and quantum information. Recent developments in the source engineering are drawing the attention from the conventional sources to waveguided setups.

One of the advantages of waveguided PDC is the discrete mode propagation of signal, idler and pump in contrast to a continuum of spatial modes in bulk crystals. Therefore, an increase in collection efficiency over several orders of magnitude is expected.

We investigate the multimode PDC in waveguided periodically poled KTP structures. Our study of the spectral and spatial structure of the twin beams reveals a profound mapping from the spatial mode propagation into the frequency distribution of the generated biphotonic states: The disjoint spectral correlations are imprinted in the spectral marginal distributions of the generated PDC states.

Our results indicate that several spatial modes can be simultaneously excited in a waveguide. The discovered modal structures have to be taken into account when designing quantum information experiments: On the one hand our findings result in the need of additional filtering to shape the PDC states. On the other hand these effects can be utilized as a multiplexed source of entangled photon pairs.