Hybrid photonic-plasmonic cavity design for very large purcell factors at telecommunication wavelengths

Hybrid photonic-plasmonic cavities can be tailored to display high Q factors and extremely small mode volumes simultaneously, which ultimately results in large values of the Purcell factor, FP. Amongst the different hybrid configurations, those based on a nanoparticle-on-a-mirror plasmonic cavity provide one of the lowest mode volumes, though so far their operation has been constrained to wavelengths below 1μm. Here, we propose a hybrid configuration consisting of a silicon photonic crystal cavity with a slot at its center in which a gold nanoparticle is introduced. This hybrid system operates at telecom wavelengths and provides high Q-factor values (Q≈105) and small normalized mode volumes (Vm≈10−4), leading to extremely large Purcell-factor values, FP≈107−108. The proposed cavity could be used in different applications such as molecular optomechanics, bio- and chemosensing, efficient quantum emitters, or enhanced Raman spectroscopy in the relevant telecom-wavelength regime.A.B. is grateful for financial support by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) through the International Research Training Group (IRTG) 2675 “Meta-ACTIVE,” Project No. 437527638. L.M. is grateful for financial support from the Next Generation European Union program, Ministerio de Universidades (Gobierno de España). A.M. acknowledges funding from H2020 European Commission (THOR-H2020-EU-829067) and the Generalitat Valenciana (PROMETEO/2019/123). M.Z.H. and J.A. acknowledge the Spanish Ministry of Science (Project No. PID2019-107432GB-I00) for financial support and grant IT1526-22 for consolidated university groups of the Basque Government.Peer reviewe