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Proceedings Paper

Spectral and spatial effects in spontaneous parametric down-conversion with a focused pump
Author(s): W. P. Grice; R. S. Bennink; Z. Zhao; K. Meyer; W. Whitten; R. Shaw
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Paper Abstract

Photons produced in the process of spontaneous parametric down-conversion (SPDC) are typically entangled in multiple degrees of freedom. Although polarization is often the parameter of interest, the presence of spectral or spatial entanglement can complicate experiments, either by reducing the visibility of certain interference effects or by reducing collection efficiency. Several recent works have shown that the collection efficiency can be improved by focusing the pump beam. This approach has the added benefit of increasing the bandwidths of the emitted photons. We show that, in the case of type II SPDC, a focused pump can result in different spatial profiles for the signal and idler. If the crystal is configured for emission of polarization-entangled photon pairs, this effect will reduce the fidelity of that entanglement. Moreover, this spatial asymmetry leads to different spectral profiles for the two photons, even when the pump is monochromatic. The spectral and spatial asymmetries can be attributed to the difference in the angular dispersion (walkoff) of the two polarizations, along with a strong correlation between wavelength and emission direction. We also examine the link between spatial entanglement and single-mode coupling efficiency. We find that efficiency is maximized when spatial entanglement can be eliminated. For the case in which walk-off does not play a role, this can be accomplished by properly focusing the pump.

Paper Details

Date Published: 5 September 2008
PDF: 11 pages
Proc. SPIE 7092, Quantum Communications and Quantum Imaging VI, 70920Q (5 September 2008); doi: 10.1117/12.795102
Show Author Affiliations
W. P. Grice, Oak Ridge National Lab. (United States)
R. S. Bennink, Oak Ridge National Lab. (United States)
Z. Zhao, Oak Ridge National Lab. (United States)
K. Meyer, Oak Ridge National Lab. (United States)
W. Whitten, Oak Ridge National Lab. (United States)
R. Shaw, Oak Ridge National Lab. (United States)

Published in SPIE Proceedings Vol. 7092:
Quantum Communications and Quantum Imaging VI
Ronald E. Meyers; Yanhua Shih; Keith S. Deacon, Editor(s)

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