Figuring process of potassium dihydrogen phosphate crystal using ion beam figuring technology

Area of Science:

• Materials Science
• Optical Engineering
• Surface Metrology

Background:

• Ion beam figuring (IBF) is a non-contact, fluid-free process beneficial for KDP crystal manufacturing.
• Conventional IBF causes heating and potential cracking in KDP crystals due to ion beam energy deposition.
• Oblique incident IBF (OI-IBF) presents advantages like reduced heat deposition and improved removal rates over normal incidence.

Purpose of the Study:

• To investigate the feasibility and effectiveness of oblique incident ion beam figuring (OI-IBF) for potassium dihydrogen phosphate (KDP) crystals.
• To analyze removal rates and removal functions under varying incident angles for OI-IBF on KDP.
• To experimentally validate the OI-IBF process for precision figuring of large KDP crystals.

Main Methods:

• Investigated removal rates and removal functions at different incident angles for OI-IBF.
• Conducted experiments to measure heat deposition on KDP test samples during OI-IBF.
• Applied OI-IBF to a 200mm x 200mm x 12mm KDP crystal over three iterative cycles.

Main Results:

• Removal rates and removal functions were characterized at various incident angles.
• Experimental heat deposition measurements were obtained for the OI-IBF process.
• Surface error on a large KDP crystal was reduced from PV 1.986λ RMS 0.438λ to PV 0.215λ RMS 0.035λ after three iterations.

Conclusions:

• Oblique incident ion beam figuring (OI-IBF) is a viable and effective technology for figuring KDP crystals.
• OI-IBF demonstrates superior performance in terms of reduced heat deposition and enhanced surface quality compared to traditional IBF.
• The study validates OI-IBF as a precise and efficient method for fabricating high-quality KDP optical components.