Monochromatic Multimode Antennas on Epsilon-Near-Zero Materials

摘要

Optical antennas couple propagating optical fields into confined modes. The spectral position and spatial extent of the confined modes are most often engineered via the design of the antenna. However, while often relegated to a secondary role, the dielectric environment can drastically alter the optical response of antennas. Here, antennas on an epsilon-near-zero materiala material with a vanishing permittivityare fabricated and characterized, demonstrating pinning of the fundamental antenna mode and the two subsequent harmonics to a narrow wavelength range. The spectral pinning of multiple modes results in what is a nearly monochromatic, yet multimode, response for the system. Coupling of these modes to the epsilon-near-zero Berreman mode supported by the thin epsilon-near-zero material is also observed. The response of the coupled system is observed experimentally and simulated using finite element methods. A coupled resonator model is developed to intuitively model the optical response of the system. The results presented here offer a mechanism for engineering the optical response of antenna systems by engineering the local dielectric environment, with potential applications in sensing, imaging, infrared optoelectronics, and thermal emission control.