Nonlinearity measurements of thin films by third-harmonic-generation microscopy

Area of Science:

• Nonlinear optics
• Materials science
• Surface science

Background:

• Nonlinear susceptibility (chi(3)) is crucial for understanding material optical properties.
• Accurate measurement of chi(3) in thin films is challenging.
• Third harmonic generation (THG) is a nonlinear optical phenomenon sensitive to material properties.

Purpose of the Study:

• To develop a simple and alternative method for measuring the electronic part of chi(3) in thin films.
• To utilize third harmonic microscopy for this purpose.
• To validate the method using reference liquid films.

Main Methods:

• Excitation of third harmonic generation (THG) using a femtosecond laser beam.
• Focusing the laser beam at the interface between the thin film and a reference layer.
• Deducing the chi(3) value from THG intensity measurements and a classical model.

Main Results:

• Demonstrated the feasibility of measuring the electronic part of chi(3) in thin films via third harmonic microscopy.
• Successfully validated the method by testing reference liquid films.
• Established the simplicity and alternative nature of the developed technique.

Conclusions:

• Third harmonic microscopy offers an accessible approach for quantifying thin film nonlinear susceptibility.
• The method provides a reliable alternative for characterizing electronic nonlinear optical properties.
• This technique has potential applications in thin film characterization and materials science.