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arXiv:1404.1192 · Journal of the Optical Society of America B

Tuning curve of type-0 spontaneous parametric down-conversion

Stefan Lerch, Bänz Bessire, Christof Bernhard, Thomas Feurer, André Stefanov

Published Mar 13, 2013• 24 citations
arXivHTMLPDF

Abstract

We study the tuning curve of entangled photons generated by type-0 spontaneous parametric down-conversion in a periodically poled potassium titanyl phosphate crystal. We demonstrate the X-shaped spatiotemporal structure of the spectrum by means of measurements and numerical simulations. Experiments for different pump waists, crystal temperatures, and crystal lengths are in good agreement with numerical simulations.

DOI
10.1364/josab.30.000953

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We theoretically investigate the properties of extended phase-matching (EPM) for spontaneous parametric down-conversion (SPDC) in four kinds of potassium titanyl phosphate isomorphs ( i.e. , KTiOPO 4 , KTiOAsO 4 , RbTiOPO 4 , and RbTiOAsO 4 crystals). The technique is based on Type II 2nd-order nonlinear optic interaction in periodically poled ferroelectric domain structures, where a single photon with a frequency of 2 ω generates a pair of photons with frequencies of ω that are orthogonally polarized with respect to each other. Under EPM, both quasi-phase matching (QPM) and group velocity (GV) matching between interacting waves are efficiently satisfied for the generation of a pair of polarization-entangled bi-photon states with frequencies of ω . Our simulation results show that the generated photon pairs have broad spectral bandwidths of over 69 - 95 nm in tele-communication bands, which are much broader than those of the typical non-EPM case ( e.g. , ~ sub-nm bandwidth when only the QPM, not the GV matching, is achieved). We will describe the EPM properties of the four kinds of KTP isomorphs in terms of interaction type, GV matching wavelength, domain poling period, and spectral bandwidth. We highlight that the KTP isomorphs have nice potential as suitable components for constituting new quantum information processing systems.

Journal of the Korean Physical Society•Sep 1, 2015•4 citations
We study the tuning curve of entangled photons generated by type-0 spontaneous parametric down-conversion in a periodically poled potassium titanyl phosphate crystal. We demonstrate the X-shaped spatiotemporal structure of the spectrum by means of measurements and numerical simulations. Experiments for different pump waists, crystal temperatures, and crystal lengths are in good agreement with numerical simulations.
The understanding of the spatiotemporal structure of the spectrum is of importance for all applications where entanglement in energy is the relevant degree of freedom and allows optimizing the spectrum for specific applications. Here, we consider spontaneous parametric down-conversion (SPDC) induced by an undepleted monochromatic pump beam of angular frequency ωρwith a transverse field distribution εp+(qp), which propagates along the z-axis of a periodically poled potassium titanyl phosphate (PPKTP) crystal. The pump photon (p) is down-converted into the idler (i) and signal (s) photon with frequency ω;= ωρ- ωsand ωs, respectively.
We study the spectral properties of spontaneous parametric down-conversion (SPDC) in a periodically poled waveguided structure of potassium-titanyl-phosphate (KTP) crystal pumped by ultrashort pulses. Our theoretical analysis reveals a strongly entangled and asymmetric structure of the two-photon spectral amplitude for type-II SPDC. We confirm these predictions experimentally by measuring single-photon spectra, on one hand, and the dependence of Hong-Ou-Mandel interference visibility on the width of spectral filtering, on the other hand.
The Periodically Poled Potassium Titanyl Phosphate (PPKTP) is a type of non linear crystal that serves as a source of production of entangled pairs of photons. The produced pair of photons, known as the Signal and Idler photons, possess unique characteristics within their entanglement that allow the production of new technologies such as quantum cryptography and quantum teleportation. The creation of the Signal and Idler photons occur through a process named Spontaneous Parametric Down Conversion (SPDC), which occurs when the pump laser beam penetrates a non linear medium. SPDC follows conservation of momentum and energy, thus imposing phase matching conditions on the generated photon pairs. These conditions result in specific space and frequency correlations of the photons. The aim of this project is to characterize the entangled photon pairs in their spatial profile and frequency spectrum, known as the Joint Spectrum.
We theoretically investigate the properties of extended phase-matching (EPM) for spontaneous parametric down-conversion (SPDC) in four kinds of potassium titanyl phosphate isomorphs ( i.e. , KTiOPO 4 , KTiOAsO 4 , RbTiOPO 4 , and RbTiOAsO 4 crystals). The technique is based on Type II 2nd-order nonlinear optic interaction in periodically poled ferroelectric domain structures, where a single photon with a frequency of 2 ω generates a pair of photons with frequencies of ω that are orthogonally polarized with respect to each other. Under EPM, both quasi-phase matching (QPM) and group velocity (GV) matching between interacting waves are efficiently satisfied for the generation of a pair of polarization-entangled bi-photon states with frequencies of ω . Our simulation results show that the generated photon pairs have broad spectral bandwidths of over 69 - 95 nm in tele-communication bands, which are much broader than those of the typical non-EPM case ( e.g. , ~ sub-nm bandwidth when only the QPM, not the GV matching, is achieved). We will describe the EPM properties of the four kinds of KTP isomorphs in terms of interaction type, GV matching wavelength, domain poling period, and spectral bandwidth. We highlight that the KTP isomorphs have nice potential as suitable components for constituting new quantum information processing systems.