Photothermal method for absorption measurements in anisotropic crystals

Area of Science:

• Optics
• Materials Science
• Thermal Analysis

Background:

• Accurate measurement of photo-thermal absorption is crucial for understanding laser-material interactions.
• Existing methods often struggle to differentiate between surface and bulk absorption, especially in anisotropic media.
• Anisotropic optical media present unique challenges due to their directional properties.

Purpose of the Study:

• To extend a quantitative photo-thermal absorption measurement system to anisotropic optical media.
• To precisely monitor wavefront deformations caused by laser irradiation.
• To develop a method for distinguishing and quantifying surface versus bulk absorption losses.

Main Methods:

• Utilized a highly sensitive Hartmann-Shack wavefront sensor for precise on-line monitoring.
• Employed a collimated test beam transmitted perpendicularly through laser-irradiated cuboid samples.
• Calibrated the system using thermal theory to interpret transient wavefront distortions.

Main Results:

• Successfully extended the measurement system to anisotropic optical media.
• Quantitatively determined both surface and bulk contributions to photo-thermal absorption.
• Presented results for KTP (Potassium Titanyl Phosphate) and BBO (Beta Barium Borate) single crystals.

Conclusions:

• The developed system provides a quantitative measure of absorption losses in anisotropic materials.
• The method effectively differentiates between surface and bulk absorption.
• This technique is valuable for characterizing optical materials used in laser applications.