Extreme ultraviolet performance of a multilayer coated high density toroidal grating

Area of Science:

• Optics and Photonics
• Materials Science
• Astrophysical Instrumentation

Background:

• Diffraction gratings are essential optical components for spectral analysis.
• Enhancing efficiency in the extreme ultraviolet (EUV) spectrum is challenging due to material limitations.
• Multilayer coatings offer a promising route to improve grating performance.

Purpose of the Study:

• To evaluate the performance of a multilayer coated diffraction grating at EUV wavelengths.
• To assess the impact of an Iridium/Silicon (Ir/Si) multilayer coating on grating efficiency and spectral resolution.
• To compare the performance of the coated grating with a standard gold-coated replica grating.

Main Methods:

• A ten-layer Ir/Si multilayer coating was applied to a 3600-lines/mm blazed toroidal replica grating.
• Absolute efficiency and spectral resolution were measured at EUV wavelengths.
• Performance was evaluated near the design wavelength of approximately 30 nm in first order.

Main Results:

• A nine-fold enhancement in peak efficiency was achieved with the Ir/Si multilayer coating.
• The measured peak EUV efficiency reached 3.3%.
• Efficiency improvements were observed across the 25-35 nm spectral range, outperforming the gold-coated grating.
• Excellent quasistigmatic spectral resolution, greater than 5000, was maintained.

Conclusions:

• Ir/Si multilayer coatings can significantly enhance the efficiency of diffraction gratings in the EUV spectrum.
• The applied coating improved efficiency without compromising spectral resolution.
• This technology holds promise for advancing EUV spectroscopy and imaging applications.