Ultra-Precision Cutting and Characterization of Reflective Convex Spherical Blazed Grating Elements

Area of Science:

• Optics and Photonics
• Materials Science
• Precision Engineering

Background:

• Convex spherical blazed gratings are crucial optical components.
• Machining accuracy and material properties significantly impact diffraction efficiency.
• Existing fabrication methods require optimization for enhanced performance.

Purpose of the Study:

• To determine optimal structure size and machining accuracy for convex spherical blazed gratings.
• To analyze the influence of tool nose radius and Poisson burr on diffraction efficiency.
• To compare the performance of different workpiece materials (RSA6061 and RSA6061+NiP) for grating fabrication.

Main Methods:

• Utilized a four-axis ultra-precision machining system.
• Determined grating unit structure size and machining accuracy based on diffraction principles.
• Analyzed effects of tool nose radius and Poisson burr on diffraction efficiency.
• Compared grating performance using RSA6061 and RSA6061+NiP materials.

Main Results:

• Achieved a blaze angle error of 0.74% in the equal-along-projection layout.
• Obtained an average surface roughness below 5 nm, meeting processing requirements.
• The equal-along-projection layout demonstrated higher diffraction efficiency.
• RSA6061+NiP material exhibited superior performance regarding Poisson burr and surface roughness.

Conclusions:

• The equal-along-projection layout enhances diffraction efficiency due to improved blaze angle accuracy.
• RSA6061+NiP is a more suitable material for fabricating convex spherical blazed gratings for SWIR Offner-type spectrometers.
• Optimized machining parameters and material selection are key for high-performance blazed gratings.