UV spectral filtering by surface structured multilayer mirrors

Area of Science:

• Optics and Photonics
• Materials Science

Background:

• Extreme ultraviolet (EUV) light sources often emit unwanted longer wavelength radiation.
• Achieving spectral purity is crucial for applications utilizing EUV light.

Purpose of the Study:

• To develop a surface-structured multilayer mirror for simultaneous UV suppression and EUV high reflectance.
• To demonstrate a fabrication method for such a mirror structure.

Main Methods:

• Fabrication of a multilayer mirror featuring silicon (Si) pyramid surface structures.
• Utilizing the differential optical properties of Si pyramids for UV reflection and EUV transparency.
• Employing blazed diffraction, interference, and absorption for UV light filtering.

Main Results:

• The developed mirror achieved full band suppression of ultraviolet (UV) light (100-400 nm).
• High reflectance for extreme ultraviolet (EUV) light at 13.5 nm was demonstrated.
• An average UV suppression factor of 14 times was recorded.
• EUV reflectance reached 56.2% at 13.5 nm.

Conclusions:

• The surface-structured multilayer mirror provides an effective spectral purity solution for XUV sources.
• The straightforward deposition technique enables robust fabrication of these mirrors.
• This technology is applicable to various XUV sources emitting longer wavelengths.