Subdiffraction Confinement in All-Semiconductor Hyperbolic Metamaterial Resonators

Abstract

The strong optical anisotropy of hyperbolic metamaterials has enabled remarkable optical behavior such as negative refraction, enhancement of the photonic density of states, anomalous scaling of resonators, and super-resolution imaging. Resonators fashioned from these optical metamaterials support the confinement of light to dimensions much smaller than the diffraction limit. These ultrasmall resonators can be used to increase light–matter interactions for new applications in photonics. Here, we present subdiffraction mid-infrared resonators based on all-semiconductor hyperbolic metamaterials. Importantly, these resonators are fully compatible with epitaxial growth techniques and can be engineered to incorporate quantum well intersubband transitions that are degenerate with the mode of the resonators, enabling an entirely new generation of quantum optoelectronic devices. The strongest optical confinement achieved is λ/33 for a free-space wavelength of 10 μm, and the measured Q-factors are in the range of 14–17. The dispersion of the resonance mode is presented through both experimental data and numerical solutions, and greater than 10% tuning of the resonance frequency (106 cm–1) is demonstrated. Radiation patterns and radiative Q-factors are also mapped out using experimental results. Finally, the resonator structures are investigated with finite element simulations and the field profile indicates the presence of a strong vertical polarization, which is essential for coupling to intersubband transitions in quantum well structures. These extreme subdiffraction resonators could be useful for engineering novel light-matter interactions and devices in the mid-infrared.

Polariton panorama

“…These modes exist over a range of frequencies where the in-plane permittivity and the out-of-plane (c-axis) permittivity are of the opposite sign. Hyperbolic electrodynamics and hyperbolic polaritons can originate from a variety of physical processes including phonons [219,223,[228][229][230][231][232][233][234][235][236][237] intersubband transitions in quantum wells [238][239][240] plasmons [220,226,[241][242][243][244], excitons [245], and Cooper pairs (see Cooper pair polaritons). Hyperbolic polaritons dramatically enhance the local photonic density of states and are predicted to give rise to strong nonlinearities [246].…”

Recent Advances in Vertically Aligned Nanocomposites with Tunable Optical Anisotropy: Fundamentals and Beyond

“…Such anisotropy is normally achieved by coupling dielectric and metallic components at nanoscale as wire-in-matrix or multilayered schemes, which find applications in sensing, spontaneous emission, negative refraction, or designs of superlenses [14][15][16]. The multilayered HMMs can be further patterned into double-fishnet nanostructures (Figure 1c) for tunable negative refraction, or nanoresonator array (Figure 1d) that is completely fabricated with semiconductor candidates [17][18][19][20][21]. Wire metamaterial, on the other hand, provides additional flexibility, such as density or distribution (Figure 1f), aspect ratio, as well as geometry of the nanowires [8,[22][23][24][25].…”

Strong Coupling in Microcavity Structures: Principle, Design, and Practical Application

“…Light fields in microcavities can contribute to ≈20‐fold enhancement for low finesse cavities, up to as much as ≈400‐fold for high finesse cavities. Therefore, scattered and incident Raman scattering field effects can be enhanced, enhancing Raman cross sections several hundred folds compared to common effects …”