Multilayered Ru/TiO2 hyperbolic material for nonlinear optics

In this work we present the design, fabrication and study of the optical properties of hyperbolic materials based on multilayered metal–dielectric Ru/TiO${}_2$ structures. The samples were fabricated using the Atomic Layer Deposition technique, and their structure was designed to have an Epsilon Near Zero point near 800 nm to match the laser wavelength employed to study their response. The linear optical properties were studied using spectrophotometry and spectral ellipsometry. The nonlinear response was studied as a function of incident irradiance using the z-scan technique with fs pulses as a function of wavelength throughout the visible, allowing the determination of the refractive and absorptive contributions to the nonlinear response. Given that a high pulse repetition rate was employed, cumulative pulse to pulse thermal effects can be present, because of this, a modification of the z-scan technique allowed the resolution of the electronic and thermal contributions to the response.