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ABSTRACT:
Howard Padmore and colleagues at Berkeley Lab have invented an Ultra-High Density Diffraction Grating that reaches extremely high resolving powers and a technique for fabricating such gratings. This is the only technology that produces ultra-high diffraction gratings suitable for soft x-ray applications. The researchers have demonstrated that an extremely high diffraction intensity (>40%) and resolution of 106 are possible. The technology provides a unique way to fabricate a diffraction grating with controllable ultra-high density grooves.
The Berkeley Lab technology employs a combination of precision lithography, anisotropic etching of silicon, multilayer coating, and chemical-mechanical polishing.
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| How an Ultra-High Density Grating is made: 1) fabrication of a near atomically perfect, low-resolution eschellette grating; 2) deposition of a multilayer coating with alternating materials and nm layer thickness; 3) polishing to reveal the periodic structure with the period determined by the bilayer spacing and slice angle value. |
The Berkeley Lab Ultra-High Density Diffraction Grating can be used in spectroscopy as a high resolution, dispersing element and can optimize the intensity, resolution, and size of a spectrometer or monochromator or any combination of the three to a factor of ~30. More specifically, the Berkeley Lab method can be applied to extreme UV and soft X-ray diffraction up to keV energies. It can also be used for nanofacet lithography.
The Berkeley Lab technique used to fabricate the Ultra-High Density Grating is useful in constructing linear templates with lines of reactive surfaces. These templates can then be used to direct self-assembly of nanocrystals or polymers. They can be applied to any application that uses ultra-high density, periodically alternating lines with different properties. This includes temporal pulse compression where a radiation pulse with a broad temporal distribution and chirped in wavelength with respect to time can be compressed to a much shorter pulse.
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