Third and fifth order nonlinear susceptibilities in thin HfO₂ layers

Area of Science:

• Materials Science
• Nonlinear Optics
• Solid State Physics

Background:

• Third harmonic generation (THG) is a key nonlinear optical process.
• Understanding nonlinear optical properties of dielectric materials is crucial for photonic applications.
• Previous studies have focused on lower-order nonlinearities in thin films.

Purpose of the Study:

• To investigate third harmonic generation (THG) in HfO2 dielectric layers.
• To quantify the third-order nonlinear susceptibility (χ(3)) and the fifth-order nonlinear susceptibility (χ(5)) in HfO2.
• To elucidate the influence of the substrate on THG in layered dielectric materials.

Main Methods:

• Fabrication of a thin gradient of Hafnium Oxide (HfO2) with continuously increasing thickness.
• Detailed investigation of the third harmonic generation process.
• Spectroscopic analysis at a fundamental wavelength of 1030 nm.

Main Results:

• Successfully quantified the third-order nonlinear susceptibility (χ(3)) of the HfO2 layers.
• Achieved the first measurement of the fifth-order nonlinear susceptibility (χ(5)) in thin dielectric layers.
• Demonstrated the influence of the substrate on the THG process.

Conclusions:

• The gradient HfO2 layer technique provides a detailed method for studying nonlinear optical properties.
• The fifth-order nonlinear susceptibility (χ(5)) in thin dielectric layers can be measured.
• Substrate effects play a significant role in third harmonic generation from dielectric layers.