Abstract
Abstract The coupling between multiple nanocavities in close vicinity leads to the hybridization of their modes. Stacked metal-insulator-metal (MIM) nanocavities constitute a highly versatile and very interesting model system to study and engineer such mode coupling, as they can be realized by lithography-free fabrication methods with fine control on the optical and geometrical parameters. The resonant modes of such MIM cavities are epsilon-near-zero (ENZ) resonances, which are appealing for nonlinear photophysics and a variety of applications. Here, we study the hybridization of ENZ resonances in MIMIM nanocavities, obtaining a very large mode splitting reaching 0.477 eV, Q-factors of the order of 40 in the visible spectral range, and fine control on the resonance wavelength and mode linewidth by tuning the thickness of the dielectric and metallic layers. A semiclassical approach that analyzes the MIMIM structure as a double quantum well system allows to derive the exact analytical dispersion relation of the ENZ resonances, achieving perfect agreement with numerical simulations and experiments. Interestingly, the asymmetry of the mode splitting in a symmetric MIMIM cavity is not reflected in the classical model of coupled oscillators, which can be directly related to quantum mechanical tunneling for the coupling of the two cavities. Interpreting the cavity resonances as resonant tunneling modes elucidates that they can be excited without momentum matching techniques. The broad tunability of high-quality ENZ resonances together with their strong coupling efficiency makes such MIMIM cavities an ideal platform for exploring light-matter interaction, for example, by the integration of quantum emitters in dielectric layers.
Highlights
The design of photonic nanocavities with tunable resonance wavelengths is of fundamental interest for many purposes in optics
To gain deeper insight into the optical properties of such MIMIM cavities, we present a semiclassical analysis of their resonant modes, which demonstrates that the MIMIM cavity can be viewed as a double quantum well
The curve of ε′ crosses the zero at four wavelengths, two of which are characterized by a small imaginary part, which renders them high-quality ENZ modes. Such ENZ resonances correspond to FerrellBerreman modes that occur naturally in thin Ag films and that can be designed within certain spectral bands in layered metamaterials [5, 38]
Summary
The design of photonic nanocavities with tunable resonance wavelengths is of fundamental interest for many purposes in optics. High-quality factors are difficult to achieve [9], intrinsic losses caused by the metals set a limit for light amplification, and possibly the integration with other systems is highly demanding due to the elaborate three-dimensional shapes of the plasmonic resonators In this respect, nanocavities with epsilon-near-zero (ENZ) resonances are a promising alternative, as in this case the imaginary part of the effective dielectric permittivity at their resonances is small [5], and ENZ nanocavities with possibly multiple tunable resonances with highquality factor could constitute a promising alternative as photonic resonators. Nanocavities with epsilon-near-zero (ENZ) resonances are a promising alternative, as in this case the imaginary part of the effective dielectric permittivity at their resonances is small [5], and ENZ nanocavities with possibly multiple tunable resonances with highquality factor could constitute a promising alternative as photonic resonators Toward such tunable cavities, the coupling of resonators provides a viable approach that enables to tailor the optical response, as coupled resonators manifest a splitting of their resonant modes [10–13]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
