Manufacturing-Enabled Tunability of Linear and Nonlinear Epsilon-Near-Zero Properties in Indium Tin Oxide Nanofilms

Abstract

Epsilon-near-zero (ENZ) materials have attracted great interest due to their exotic linear and nonlinear responses, which makes it significant to tune ENZ wavelengths for wavelength-dependent applications. However, studies to achieve tunability in a wide spectral range and link the fabrication parameters with linear and nonlinear ENZ properties have been uncovered. ENZ indium tin oxide (ITO) nanofilms are fabricated by magnetron sputtering, through which the control of ENZ properties is demonstrated. Factors in the sputtering process, such as the gas ratio and annealing, have a great impact on the ITO samples. Tunable ENZ parameters are listed to provide a beneficial database for ENZ ITO, mainly attributed to the change of carrier concentration. The influence of ENZ parameters on optical characteristics via annealing treatment is further explored. The ENZ wavelength is blue-shifted by 609 nm, and the intrinsic loss is reduced by 63.2%, while the ITO samples exhibit better linear scattering properties and stronger field intensity enhancement. Additionally, the laser testing system illustrates the change from reverse saturable absorption to saturable absorption with an absolute modulation depth of 21.9%, improved by 222.1%, and the nonlinear refractive index n 2 and nonlinear absorption coefficient β are 2.07 × 10–16 m2 W–1 and −3.16 × 10–10 m W–1 for post-annealed ITO samples, respectively. The proposed sputtering protocol offers a feasible technique to control the linear and nonlinear ENZ performance, which has great potential in laser technology and nanophotonics.

Oxygen Vacancy Controlled Hyperbolic Metamaterial based on Indium Tin Oxide (ITO) Nanotubes with Switchable Optical Properties

“…35 The most common technique for the deposition of ITO with optical quality are physical vapor deposition (PVD) processes. 33,39,40 However, for creating 3D bulk metamaterials, for example, PVD is not applicable by a template-based approach since the penetration depth of the deposited TCO into the nanoscale templates is limited. Liquid phase deposition (LPD) offers an alternative to preparing 3D bulk metamaterials in a template-based approach.…”