3D Meta-Atoms for High Confinement of Mid-IR Radiation

The ability to confine photons into structures with highly sub-wavelength volumes is extremely interesting for many applications such as sensing, nonlinear optics, and strong light-matter interactions. However, their realization is increasingly difficult as the wavelength becomes shorter, due to fabrication challenges and increased metal losses. In this work, the first experimental characterization of 3D circuit-like resonators operating in the mid-infrared is presented. Through a combination of simulations, reflectivity measurements, and scanning near-field optical microscopy, an analytical model capable of predicting the electromagnetic response of these structures based on their geometrical parameters is developed. The studied design offers a high degree of flexibility, enabling precise control over the resonant frequency of the various modes supported by the resonator, as well as independent control over radiative and non-radiative losses. Combined with the extreme field confinement demonstrated, these meta-atoms are highly promising for applications in detectors, emitters, nonlinear processes, and strong light-matter coupling.