At EUV wavelengths, the coating is the optical engine
At 13.5 nm, most materials absorb strongly. A useful mirror depends on a precisely tuned multilayer stack, typically alternating high- and low-index materials so reflections reinforce each other at the target wavelength.
The practical challenge is discipline: layer thickness, interface roughness, substrate figure, and capping strategy all influence usable reflectivity and lifetime. A small deviation can shift the peak wavelength or reduce system throughput.
Key evaluation questions
- What angle of incidence and bandwidth does the system require?
- How uniform must reflectivity be across the clear aperture?
- Does the application prioritize peak reflectivity, environmental stability, or figure precision?
For lithography, metrology, HHG beam steering, and synchrotron beamlines, mirror selection should start from the optical path rather than from a generic catalog line.
