Masking technique for coating thickness control on large and strongly curved aspherical optics

Area of Science:

• Materials Science
• Optical Engineering
• Thin Film Deposition

Background:

• Controlling coating thickness on large, curved optics is challenging.
• Ion beam sputtering is a common deposition technique.
• Achieving precise thickness gradients is crucial for optical performance.

Purpose of the Study:

• To develop a method for precise control of coating thickness on large, curved optics using ion beam sputtering.
• To design an original mask system for screening sputtered materials.
• To achieve high thickness gradients in deposited layers.

Main Methods:

• Utilizing an original multielement mask design.
• Calculating the mask based on measured 2D coating thickness distribution.
• Employing an iterative process to refine the final mask design.
• Applying the technique to ion beam sputtering of tantalum pentoxide.

Main Results:

• Successfully deposited tantalum pentoxide layers with a high thickness gradient.
• Coated a 500 mm diameter curved substrate.
• Achieved residual errors in the coating thickness profile below 0.7%.

Conclusions:

• The developed mask design method enables precise control of coating thickness on large, curved optics.
• The technique is effective for creating high-thickness gradients in optical coatings.
• The method offers high accuracy for demanding optical applications.