Modeling the image quality of enhanced reflectance x-ray multilayers as a surface power spectral density filter...

Area of Science:

• Optics and Materials Science
• Surface Science and Thin Films

Background:

• High-performance optical systems require precise control of residual surface roughness across all spatial frequencies.
• Enhanced reflectance multilayers demand both high reflectance and high spatial resolution, making surface roughness a critical parameter.

Purpose of the Study:

• To model multilayer coatings as a surface power spectral density (PSD) filter function.
• To investigate the impact of interface correlation on multilayer optical performance.
• To apply linear systems techniques for evaluating image quality and optical fabrication tolerances.

Main Methods:

• Modeling multilayer interfaces as uncorrelated at high spatial frequencies (microroughness) and correlated at lower frequencies.
• Treating the multilayer coating as a surface power spectral density (PSD) filter.
• Applying linear systems analysis to understand the filtering effect on substrate PSD.

Main Results:

• Multilayer coatings function as a low-pass spatial frequency filter.
• The cutoff frequency of this filter is dependent on material properties and fabrication processes.
• This filtering behavior influences the overall system's spatial resolution and image quality.

Conclusions:

• The PSD filter model provides a framework for understanding multilayer optical performance.
• Linear systems techniques can be effectively used to evaluate image quality in systems with enhanced reflectance multilayers.
• This approach aids in defining optical fabrication tolerances for demanding x-ray applications.