Efficient high-order diffraction of extreme-ultraviolet light and soft x-rays by nanostructured volume gratings

We report what is believed to be the first demonstration that volume gratings diffract extreme-ultraviolet light (EUV) or soft x-rays into high orders approximately an order of magnitude more efficiently than predicted by classical thin-grating theory. At the 13-nm wavelength, copolymer grating structures with 200-nm period and aspect ratios of ~10:1 achieved diffraction efficiencies of 11.2%, 15.3%, 11.5%, and 9.1% in the orders m of 2, 3, 4, and 5, respectively. In addition, the measured transmission spectra are consistent with electrodynamic calculations by coupled-wave theory. High-order diffraction can now be employed for substantially improved diffractive EUV and x-ray optics, e.g., highly resolving diffractive lenses and large-aperture condensers.