Optimizing and characterizing grating efficiency for a soft X-ray emission spectrometer

Area of Science:

• Optics and Photonics
• Materials Science
• Spectroscopy

Background:

• Soft X-ray diffraction gratings are crucial components in various spectroscopic instruments.
• Accurate modeling of grating efficiency is essential for optimizing instrument performance.
• Existing methods often lack the flexibility to handle complex groove profiles and computational demands.

Purpose of the Study:

• To develop and validate a new open-source software for modeling soft X-ray diffraction grating efficiency.
• To design a high-efficiency, high-resolution soft X-ray emission spectrometer for the REIXS beamline.
• To investigate the impact of real-world fabrication imperfections on grating performance.

Main Methods:

• Utilized the differential method with the S-matrix propagation algorithm for efficiency calculations.
• Developed open-source software incorporating arbitrary groove profiles (e.g., from AFM data) and high-performance computing.
• Designed and characterized soft X-ray gratings, comparing measured efficiency with theoretical predictions.

Main Results:

• Achieved theoretical grating efficiency >10% and resolving power E/ΔE > 2500 (100-1000 eV) for the designed spectrometer.
• Exploited third diffraction order for a high-resolution mode (E/ΔE > 14000 at 280 eV).
• Identified discrepancies between measured and theoretical efficiencies due to fabrication errors, and developed a method to predict grating parameters.

Conclusions:

• The new software accurately models soft X-ray grating efficiency, accounting for complex profiles and real-world effects.
• The designed spectrometer meets high-efficiency and high-resolution requirements for synchrotron applications.
• A novel method for characterizing grating parameters from efficiency measurements is proposed.