Multilayered hyperbolic Au/TiO₂ nanostructures for enhancing the nonlinear response around the epsilon-near-zero point

• Fernando Arturo Araiza-Sixtos,
• Mauricio Gomez-Robles,
• Rafael Salas-Montiel and
• Raúl Rangel-Rojo

Beilstein J. Nanotechnol. 2026, 17, 251–261, doi:10.3762/bjnano.17.17

• –dielectric Au/TiO2 structures. The samples were fabricated using Joule effect evaporation for gold and electron beam evaporation for titanium dioxide. Their structure was designed to have an epsilon-near-zero (ENZ) point at different wavelengths around 800 nm, in order to study their nonlinear response as a

• , a value that is comparable to other ENZ materials in literature. Keywords: epsilon-near-zero (ENZ); hyperbolic metamaterials; nonlinear optics (NLO); Introduction In recent years, the invention of new techniques to fabricate nanostructured materials led to the creation of metamaterials. These new

• that, with the right manipulation of the geometry, we are able to make the electric permittivity near zero (“epsilon near zero”, ENZ). The ENZ point causes light to travel through the medium with constant phase, it enhances the electric field, and it enhances the nonlinear response by combining

Enhancement of X-ray emission from nanocolloidal gold suspensions under double-pulse excitation

• Wei-Hung Hsu,
• Frances Camille P. Masim,
• Armandas Balčytis,
• Hsin-Hui Huang,
• Tetsu Yonezawa,
• Aleksandr A. Kuchmizhak,
• Saulius Juodkazis and
• Koji Hatanaka

Beilstein J. Nanotechnol. 2018, 9, 2609–2617, doi:10.3762/bjnano.9.242

• [26], respectively. Theory: Epsilon-Near-Zero (ENZ)-Material A strong generation of X-rays is related to a large amount of absorbed energy and a high temperature [3][4]. In terms of relative permittivity (dielectric constant), εr, a transparent medium (water) with colloidal gold nanoparticles

• represents an effective medium with an overall positive real part of the permittivity. Upon excitation, the material is approaching dielectric breakdown and a state of εr ≈ 0 (epsilon-near-zero (ENZ) state; ). Under the ENZ condition, the strongest absorption takes place [36][37]: Here, εi is the intrinsic