Coupled harmonic oscillators model with two connected point masses for application in photo-induced force microscopy

Area of Science:

• Nanoscience and Nanotechnology
• Physical Chemistry
• Materials Science

Background:

• Photo-induced force microscopy (PiFM) is a powerful technique for nanoscale imaging.
• Existing PiFM models lack intuitiveness and a unified theoretical framework.
• Understanding PiFM's dynamic features and signal behaviors is crucial for its application.

Purpose of the Study:

• To develop a more intuitive and unified theoretical model for photo-induced force microscopy (PiFM).
• To replicate and explain the dynamic features and signal responses of PiFM.
• To elucidate the physical mechanism behind unexpected signal behaviors in PiFM's sideband coupling mode.

Main Methods:

• Developed a novel model based on coupled harmonic oscillators with two point masses and elastic wires.
• Solved the equations of motion using adjusted oscillator parameters.
• Integrated the new model with a photo-induced thermal expansion force model.

Main Results:

• Successfully replicated resonance frequencies and eigenmode shapes from previous PiFM theories.
• Accurately reproduced responses to external forces in both direct and sideband coupling modes.
• Uncovered the physical mechanism behind the peak-valley signal behavior in sideband coupling mode as a function of sample thickness.

Conclusions:

• The coupled harmonic oscillator model provides an intuitive and unified framework for understanding PiFM.
• The model successfully explains complex PiFM dynamics and signal anomalies.
• This work enhances the comprehension of PiFM operation and its potential applications in nanoscience.