Laser picosecond acoustics in a two-layer structure with oblique probe light incidence

Area of Science:

• Optics
• Acoustics
• Materials Science

Background:

• Laser picosecond acoustics is a powerful technique for probing material properties.
• Analyzing experiments with obliquely incident light in layered structures presents challenges.
• Understanding optical modulation components is crucial for accurate material characterization.

Purpose of the Study:

• To outline a theory for analyzing laser picosecond acoustics experiments.
• To calculate reflectance and phase changes in a two-layer structure.
• To differentiate optical modulation contributions from photoelastic and acoustic strain effects.

Main Methods:

• Developed a theoretical framework for oblique incidence.
• Incorporated multiple optical reflections in calculations.
• Analyzed a partially transparent layer on a substrate with arbitrary optical constants.

Main Results:

• Calculated reflectance and phase changes for the two-layer system.
• Provided a method to distinguish between photoelastic and interface displacement effects.
• The theory accounts for complex optical interactions within the sample.

Conclusions:

• The presented theory enables accurate analysis of picosecond acoustics experiments.
• It allows for the separation of different physical phenomena influencing optical signals.
• This work is vital for advanced materials research using optical pump-probe techniques.