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Q: Fachverband Quantenoptik und Photonik

Q 61: Poster Quanteneffekte

Q 61.6: Poster

Donnerstag, 22. März 2007, 16:30–18:30, Poster C

Photon correlations in broadband down-converted light — •Benjamin Freyer, Axel Heuer, and Ral Menzel — Institute of Physics, Chair of Photonics, University of Potsdam, Am Neuen Palais 10, D-14469 Potsdam

Parametric down conversion (PDC), is frequently used for the generation of correlated photon pairs in several quantum optic applications like quantum cryptography or quantum imaging. In this process the two photons of the pair are generated via the spontaneous decay of one pump photon. Both photons, signal and idler, are strongly correlated because of conservation of energy and momentum regarding their wavelength and propagation direction. The spectrum of the down-converted light, only limited by the phase matching conditions, could spread over several hundreds of nanometres.

We investigated pulsed PDC in Beta Barium Borat (BBO) crystals. The crystals are cut for type I phase matching. Type I phase matching results in emission cones of the signal and idler photons, which are centred around the propagation direction of the pump photon. The aperture angle of the cone is a function of the wavelength of signal and idler photons as well as of the angle of incidence of the pump photon. We measured the rate of coincidence for different cone angles and wavelengths. In these measurements the pump geometry and crystal length was varied. As a result we get the normalized coincidence rate as a function of the PDC spectrum and of the cone radius.