Picometre-level surface control of a closed-loop, adaptive X-ray mirror with integrated real-time interferometric
Ioana Theodora Nistea1, Simon G Alcock1, Andrew Foster2
1Optics and Metrology, Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE, United Kingdom.
Journal of Synchrotron Radiation
|December 18, 2024
Summary
This study presents a novel closed-loop adaptive mirror system for X-ray applications. The system achieves ultra-stable, atomic-level control of mirror shape, crucial for advanced optics like extreme ultraviolet lithography.
Area of Science:
- Optics and X-ray Science
- Materials Science and Engineering
- Control Systems and Metrology
Background:
- Synchrotron light and free-electron laser facilities require precise control of X-ray beams.
- Existing adaptive optics systems face challenges with stability, precision, and speed for X-ray wavefront manipulation.
- Deformable mirrors are critical components for shaping X-ray beams, but achieving sub-nanometer precision is demanding.
Purpose of the Study:
- To develop and test a closed-loop adaptive mirror system for rapid, precise, and ultra-stable X-ray beam shaping.
- To demonstrate sub-nanometer height resolution and stability in a macroscopic X-ray mirror.
- To validate the system's performance under demanding conditions, including hysteresis and environmental factors.
Main Methods:
- Utilized a piezoelectric bimorph deformable mirror with continuous optical surface monitoring via interferometric sensors at 20 kHz.
- Implemented autonomous conversion of height data to voltage commands for piezo actuators, enabling closed-loop shape modification.
- Designed a temperature-insensitive metrology frame for enhanced reference datum stability and repeatability.
Main Results:
- Achieved repeatable bending and stabilization of mirror surface components to <200 pm peak-to-valley error, irrespective of bending history.
- Demonstrated stabilization against nanometer-scale drifts observed in open-loop systems.
- Validated system robustness through over 1 million voltage cycles without damage or performance degradation.
Conclusions:
- The developed closed-loop adaptive mirror system offers unprecedented fast and precise optical control in the X-ray domain.
- The system provides real-time, hyper-precise, temperature-insensitive mirror form control with atomic-level height resolution.
- This technology is highly beneficial for optical communities, including extreme ultraviolet (EUV) lithography, requiring sub-nanometer mirror bending control.
