Mo/Si multilayer-coated amplitude-division beam splitters for XUV radiation sources

Area of Science:

• Optics and Photonics
• Materials Science
• Surface Science

Background:

• Extreme ultraviolet (XUV) radiation sources require specialized optical components for beam manipulation.
• Amplitude-division beam splitters are crucial for controlling and dividing XUV beams in various scientific applications.

Purpose of the Study:

• To develop and characterize novel amplitude-division beam splitters for XUV radiation.
• To optimize beam splitter performance for specific XUV radiation parameters and free-electron laser applications.

Main Methods:

• Deposition of Mo/Si multilayer coatings on SiN membranes.
• Optimization of multilayer structures (periodicity, number of bilayers) for reflectivity and transmissivity.
• Characterization using XUV reflectometry, transmission measurements, atomic force microscopy, and optical interferometry.

Main Results:

• Achieved flatness of 4 nm r.m.s. (3x3 mm) and 22 nm r.m.s. (10x10 mm) beam splitters.
• Surface roughness (high-spatial-frequency: 0.7-1 nm r.m.s., middle-spatial-frequency: 0.2-0.8 nm r.m.s.).
• High spatial homogeneity in reflection and transmission (<2% deviation across the optical element).

Conclusions:

• The developed Mo/Si multilayer beam splitters meet stringent requirements for XUV applications.
• Identified areas for improvement in flatness and wavefront distortion for advanced XUV free-electron laser systems.
• The characterized optical elements show excellent homogeneity and performance for XUV beam splitting.