Enhanced Nonlinearity of Epsilon-Near-Zero Indium Tin Oxide Nanolayers with Tamm Plasmon-Polariton States

Recently, 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. In particular, the ENZ behavior of indium tin oxide (ITO) thin films resulted in Kerr-type nonlinearity with non-perturbative refractive index variations that are key to developing more efficient Si-compatible devices with sub-wavelength dimensions. In this contribution, exceptional enhancement of the nonlinear index variation of 30 nm-thick ITO nanolayers by silicon dioxide/silicon nitride (SiO2/SiN) Tamm plasmon-polariton structures fabricated by radio-frequency magnetron sputtering on transparent substrates under different annealing conditions is proposed and demonstrated. In particular, the linear and nonlinear optical properties of ITO thin films and resonant photonic structures are investigated using broadband spectroscopic ellipsometry and intensity-dependent Z-scan nonlinear characterization, demonstrating enhancement of optical nonlinearity with refractive index variations as large as Delta n approximate to 2 in the non-perturbative regime. This study reveals that the efficient excitation of strongly confined plasmon-polariton Tamm states substantially boosts the nonlinear optical response of ITO nanolayers, providing a stepping stone for the engineering of more efficient infrared devices and nanostructures for a broad range of applications, including all-optical data processing, nonlinear spectroscopy, sensing, and novel quantum detection modalities. Enhancement of the nonlinear index variation Delta n of 30 nm-thick indium tin oxide (ITO) nanolayers coupled to Tamm plasmon-polariton states is experimentally demonstrated in this contribution. The linear and nonlinear optical properties of ITO materials and photonic structures are investigated using spectroscopic ellipsometry and intensity-dependent Z-scan nonlinear characterization, demonstrating Delta n approximate to 2 in the low excitation regime.image

Automated summary

This study demonstrates experimentally the enhancement of the nonlinear refractive index variation of 30 nm-thick indium tin oxide (ITO) nanolayers coupled to Tamm plasmon-polariton states. The linear and nonlinear optical properties of ITO materials and photonic structures are investigated using spectroscopic ellipsometry and intensity-dependent Z-scan nonlinear characterization, showing a refractive index variation of Delta n approximately 2 in the low excitation regime.