Analysis of the Thermo-Reflectivity Coefficient Influence Using Photothermal Pump-Probe Techniques

Area of Science:

• Physics
• Materials Science
• Optical Spectroscopy

Background:

• Photothermal techniques are increasingly used for solids and fluids due to improved modeling of thermo-optical-mechanical effects.
• Temperature variations during laser excitation can alter optical reflectivity, potentially influencing photothermal signal measurements.

Purpose of the Study:

• To investigate the impact of temperature-dependent reflectivity changes on photothermal signals.
• To analyze this effect in two specific pump-probe techniques: thermal lens and thermal mirror.
• To quantify the influence for different material types.

Main Methods:

• Derivation of a linear equation for reflectivity's temperature dependence.
• Testing the derived solution using optical properties of semi-transparent and opaque materials.
• Analysis of two photothermal techniques: thermal lens and thermal mirror.

Main Results:

• The influence of reflectivity change on photothermal signals was quantified for different materials.
• For semi-transparent materials, the effect was found to be less than 0.01%.
• For opaque materials, the influence was found to be less than 3%.

Conclusions:

• Temperature-induced reflectivity changes have a minor impact on photothermal signals in semi-transparent materials.
• The effect is more significant, though still below 3%, in opaque materials.
• Understanding this phenomenon is crucial for accurate photothermal measurements across various materials.