Laser-Assisted Diamond Turning for Anisotropy Suppression in Calcium Fluoride

Area of Science:

• Materials Science
• Optical Engineering
• Crystallography

Background:

• Single-crystal calcium fluoride (CaF2) exhibits anisotropic properties, leading to processing challenges.
• Controlling the brittle-plastic transition is crucial for precise machining of optical materials.

Purpose of the Study:

• To investigate laser-assisted cutting for controlling the brittle-plastic transition in CaF2.
• To suppress processing anisotropy in CaF2 through local thermal softening.
• To fabricate high-performance CaF2 optical microcavities with reduced orientation-dependent variations.

Main Methods:

• Nano-scratch experiments to analyze the effect of heating on the brittle-plastic transition.
• Laser-assisted ultra-precision turning for fabricating CaF2 optical microcavities.
• Surface roughness and optical quality factor (Q-factor) measurements.

Main Results:

• Heating significantly increased the critical plastic cutting depth for all crystal planes.
• Inter-plane differences in cutting behavior were substantially reduced.
• CaF2 optical microcavities with surface roughness below 10 nm were fabricated.
• A maximum Q-factor of approximately 7.79 × 10^7 was achieved.
• Performance variations among different crystal orientations were significantly minimized.

Conclusions:

• Laser-assisted cutting effectively promotes uniform plastic flow across CaF2 crystal planes.
• This method offers a viable approach for consistent, high-performance fabrication of anisotropic optical components.
• The findings are critical for advancing the manufacturing of precision CaF2 optics.