Highly Nonlinear ENZ Driven Hybrid Tamm Plasmon-Polariton Nanostructures on the Si Platform

Materials with vanishingly small permittivity, known as epsilon-near-zero (ENZ) media, emerged as promising candidates to achieve nonlinear optical effects of unprecedented magnitude on a solid-state platform. Epsilon-near-zero (ENZ) materials, characterized by an almost vanishing permittivity, exhibit a plethora of fascinating optical properties, including a significant enhancement of second- and third-order nonlinear optical processes. Combined with their CMOS compatibility, these materials have been integrated into compact photonic devices and nanostructures that perform remarkable nonlinear operations such as order-unity refractive index modulations with sub-picosecond response time, enhanced harmonic generation, ultra-fast pulse shaping through frequency translation, and optical time reversal. Recently, record-high refractive index modulation Δn≈2 has been demonstrated in silicon dioxide/silicon nitride (SiO2/SiN) Tamm plasmon-polariton (TPP) structures with embedded ITO nanolayers fabricated by radio-frequency magnetron sputtering. These nonlinear TPP structures also exhibit significant third harmonic generation and non-reciprocal characteristics. Building upon these findings, we present here the design, fabrication, and nonlinear characterization of novel hybrid TPP structures coupled to TiN plasmonic nanoantennas deposited atop nonlinear ITO nanolayers. We demonstrate that these structures feature multiple high-Q resonant modes originating from the hybridization of TPPs and the localized modes of TiN nanoantennas, leading to sub-wavelength nanoscale confinement of the electric field inside the nonlinear ITO layer at the relevant ENZ wavelengths for enhanced nonlinear optical devices on the Si chip.