Wide Field-of-View Reflection-Mode Ptychographic Imaging Microscope with Tabletop 12.7 nm High Harmonic Illumination

High-resolution imaging is an invaluable tool for understanding nanoscale systems. In particular, tabletop extreme ultraviolet (EUV) coherent diffractive imaging (CDI) techniques based on high harmonic generation (HHG) can combine femtosecond (fs) pulse durations with nanometer resolution and elemental-, spin-, electronic-and magnetic-sensitivity, proving to be an ideal probe of complex nanostructured systems [1-2].

In this work, we demonstrate a novel technique for glancing-incidence, large field-of-view, reflection-mode ptychographic imaging using a tabletop 12.7nm HHG source. To our knowledge, this is the first demonstration of reflection-mode imaging at 12.7nm on a tabletop, as well as the first ~13nm reflection-mode image using any source of an extended sample of general composition (ie., not fabricated on a multilayer mirror). In CDI, coherent illumination diffracts from a sample, and the resulting light is recorded on a camera (typically a CCD) placed far from the sample.

The phase profile of this light is lost by the CCD, resulting in the well-known phase problem [3]. The complex field can be computationally recovered and back-propagated to reconstruct the phase and amplitude of the field leaving the object. Ptychography is a robust form of CDI in which multiple diffraction patterns are recorded as the illumination is scanned, with overlap between positions, across the sample [4]. The resulting data is combined to provide the phase and amplitude of both the sample and the illumination.