Tabletop coherent diffractive imaging of extended objects in transmission and reflection geometry

Abstract

Recent breakthroughs in high harmonic generation have extended the reach of bright tabletop coherent light sources from a previous limit of ≈100 eV in the extreme ultraviolet (EUV) all the way beyond 1 keV in the soft X-ray region. Due to its intrinsically short pulse duration and spatial coherence, this light source can be used to probe the fastest physical processes at the femtosecond timescale, with nanometer-scale spatial resolution using a technique called coherent diffractive imaging (CDI). CDI is an aberration-free technique that replaces image-forming optics with a computer phase retrieval algorithm, which recovers the phase of a measured diffraction amplitude. This technique typically requires the sample of interest to be isolated; however, it is possible to loosen this constraint by imposing isolation on the illumination. Here we extend previous tabletop results, in which we demonstrated the ability to image a test object with 22 nm resolution using 13 nm light [3], to imaging of more complex samples using the keyhole CDI technique adapted to our source. We have recently demonstrated the ability to image extended objects in a transmission geometry with ≈100 nm resolution. Finally, we have taken preliminary CDI measurements of extended nanosystems in reflection geometry. We expect that this capability will soon allow us to image dynamic processes in nanosystems at the femtosecond and nanometer scale.