SAMOP 2023 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 42: Poster III

Q 42.18: Poster

Wednesday, March 8, 2023, 16:30–19:00, Empore Lichthof

Generalized Description of the Spatio-Temporal Biphoton State in Spontaneous Parametric Down-Conversion — •Baghdasar Baghdasaryan^1,2, Carlos Sevilla-Gutiérrez³, Fabian Steinlechner^3,4, and Stephan Fritzsche^1,2,4 — ¹Theoretisch-Physikalisches Institut, Friedrich Schiller University Jena, 07743 Jena, Germany — ²Helmholtz-Institut Jena, 07743 Jena, Germany — ³Fraunhofer Institute for Applied Optics and Precision Engineering IOF, 07745 Jena, Germany — ⁴Abbe Center of Photonics, Friedrich Schiller University Jena, 07745 Jena, Germany

Spontaneous parametric down-conversion (SPDC) is a widely used source for photonic entanglement. Years of focused research have led to a solid understanding of the process, but a cohesive analytical description of the paraxial biphoton state has yet to be achieved. We present a simple-to-use closed expression for the biphoton state. The approach describes the full spectral and spatial properties of all interacting beams and applies to a wide range of experimental settings. The analytical treatment of the biphoton state decomposed into discrete Laguerre Gaussian (LG) modes also provides a deeper insight into the role of the Guoy phase in PDC. Especially, the coupling strength of spatial and spectral degrees of freedom (DOF) in PDC is fully controlled by the Gouy phase of pump, signal and idler beam. The control over the Gouy phase can be used to engineer entangled state separable in spatial and spectral DOF.