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Single‐Step 3D Nanofabrication of Kinoform Optics via Gray‐Scale Focused Ion Beam Lithography for Efficient X‐Ray Focusing
Author(s) -
Keskinbora Kahraman,
Grévent Corinne,
Hirscher Michael,
Weigand Markus,
Schütz Gisela
Publication year - 2015
Publication title -
advanced optical materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.89
H-Index - 91
ISSN - 2195-1071
DOI - 10.1002/adom.201400411
Subject(s) - materials science , optics , ion beam lithography , nanolithography , lithography , fabrication , diffraction , lens (geology) , focused ion beam , optoelectronics , ion beam , beam (structure) , physics , ion , medicine , alternative medicine , pathology , quantum mechanics
A kinoform lens is a highly efficient photonic device capable of focusing a wide range of electromagnetic radiation. Unfortunately, its realization without the need of any approximation remained elusive for a very long time. A direct, simple and precise fabrication method was still missing. Here, an efficient preparation scheme is presented for the first time. Two kinoform lenses made out of polycrystalline gold and nano‐crystalline PdSi, are successfully fabricated, thoroughly characterized and tested for their ultimate focusing performances at soft X‐ray energies. The fabrication is made possible by means of gray‐scale direct‐write ion beam lithography. A first ever 2D imaging is carried out via scanning transmission X‐ray microscopy achieving resolutions down to 60 nm. The diffraction efficiency is measured to be 77% to 89% of the theoretical value and is only limited by the strong absorption at the soft X‐ray energy range. The impact of materials selection on the final quality of the lens is emphasized. The overall results enable the production of almost perfect kinoform profiles with high precision. This opens unprecedented perspectives for the focusing of soft and hard X‐rays at very high efficiencies and paves the way toward new applications in a wider energy range.