Intensity-dependent loss properties of window materials at 248 nm

Area of Science:

• Materials Science
• Optical Physics
• Laser-Induced Damage

Background:

• Understanding optical material behavior under high-intensity laser irradiation is crucial for laser system design.
• Nonlinear absorption mechanisms limit laser-induced damage thresholds and transmission efficiency.

Purpose of the Study:

• To investigate and differentiate various loss mechanisms in optical materials.
• To determine the dominant nonlinear absorption processes in fused silica, CaF(2), LiF, and MgF(2) under specific laser conditions.

Main Methods:

• Transmission measurements of fused silica, CaF(2), LiF, and MgF(2) using 450-fsec, 248-nm laser pulses.
• Systematic study of scattering, color-center formation, and multiphoton absorption as separate loss factors.

Main Results:

• Fused silica exhibits a dominant two-photon absorption mechanism.
• CaF(2), LiF, and MgF(2) show dominant three-photon absorption and absorption due to color-center formation.
• Loss mechanisms were quantified across a range of laser fluences (10-120 GW/cm(2)).

Conclusions:

• The specific nonlinear absorption pathways vary significantly between different optical materials.
• Identifying these mechanisms is essential for selecting appropriate optical materials for high-power laser applications.