SKM 2023 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 35: Focus Session: Transient multi-wave mixing on excitonic resonances

HL 35.7: Invited Talk

Thursday, March 30, 2023, 12:30–13:00, POT 251

Spontaneous parametric down-conversion in semiconductor metasurfaces — •Maria Chekhova — Max-Planck Institute for the Science of Light, Erlangen, Germany — Friedrich-Alexander Universität Erlangen-Nürnberg

Spontaneous parametric down-conversion (SPDC) is the most efficient way to generate pairs of entangled photons for quantum photonics applications such as quantum communication, quantum imaging and sensing, and quantum metrology. Today, several groups are trying to implement SPDC on nanoscale quasi-2D platforms, such as subwavelength crystalline layers and metasurfaces. These ultrathin sources have numerous advantages. They are integrable, ultrafast, ultrabroadband and, most importantly, multifunctional. Metasurfaces, in addition, can enhance the rate of photon pair generation due to their *geometric* resonances.

In my talk I will show our recent results on the generation of photon pairs in metasurfaces made of gallium arsenide and gallium phosphide. The metasurfaces are structured to support bound states in the continuum (also known as Fano) resonances, with the quality factors Q reaching several hundred. The resonances enhance the spontaneous emission of pairs by a factor on the order of Q if the frequency of one of the photons coincides with the resonance. Due to the ultrasmall thickness of such sources, SPDC can be pumped slightly above their bandgap without considerable effect of absorption. The inevitably high level of photoluminescence can be overcome by time-resolved registration of photon pairs.