Real-time and Sub-wavelength Ultrafast Coherent Diffraction Imaging in the Extreme Ultraviolet

Abstract

Coherent Diffraction Imaging is a technique to study matter with nanometer-scale spatial resolution based on coherent illumination of the sample with hard X-ray, soft X-ray or extreme ultraviolet light delivered from synchrotrons or more recently X-ray Free-Electron Lasers. This robust technique simultaneously allows quantitative amplitude and phase contrast imaging. Laser-driven high harmonic generation XUV-sources allow table-top realizations. However, the low conversion efficiency of lab-based sources imposes either a large scale laser system or long exposure times, preventing many applications. Here we present a lensless imaging experiment combining a high numerical aperture (NA = 0.8) setup with a high average power fibre laser driven high harmonic source. The high flux and narrow-band harmonic line at 33.2 nm enables either sub-wavelength spatial resolution close to the Abbe limit (Δr = 0.8λ) for long exposure time, or sub-70 nm imaging in less than one second. The unprecedented high spatial resolution, compactness of the setup together with the real-time capability paves the way for a plethora of applications in fundamental and life sciences.

Exploring new avenues in high repetition rate table-top coherent extreme ultraviolet sources

“…Additionally, the demonstrated repetition rate has previously been only accessible with enhancement cavities 23 . The achievement of efficient HHG with low-energy and high repetition rate laser systems has profound implications for a diverse field of HHG applications, e.g., in (multi)-dimensional surface science 48 , coincidence detection 7 , or coherent diffractive imaging 6,49 . Moreover, this experimental demonstration paves the way for making HHG sources more compact, cost-effective, reliable, and accessible to non-laser experts (e.g., by replacing our front-end (CC-FCPA) with a compact turn-key fiber laser system 33,34 or a thin-disk oscillator 35,36 ).…”

“…The latter challenge is particularly important for photoelectron spectroscopy and microscopy in which space-charge effects need to be avoided 3,4 . Other possible applications are coherent diffractive imaging 5,6 , coincidence experiments 7 , or frequency metrology, in which multi-10 MHz lasers with a stabilized frequency comb are used 8 . Generally, there is a great demand for compact, cost-effective and reliable sources that can also be used by scientists who are not laser experts, which would severely broaden their applications.…”

Online Monitoring of Laser-Generated XUV Radiation Spectra by Surface Reflectivity Measurements with Particle Detectors

“…Due to the spectral, spatial, and temporal properties of HHG radiation, its applications range from fundamental atomic and molecular physics to material science, biology, and medicine [1][2][3], and great effort is being put into further source development [4][5][6] and scaling to high repetition rates and high laser pulse energies [7,8]. Since high-order harmonics are generated from an infrared laser pulse by nonlinear interaction with a gaseous medium, one task is to filter out the fundamental infrared beam to ensure a pure interaction of the sample with XUV radiation [9][10][11].…”

A desktop extreme ultraviolet microscope based on a compact laser-plasma light source

“…These facilities, although state of the art and dedicated to cutting-edge science experiments, are not "user friendly," with limited user access and require high maintenance costs, because of their scale and complexity. Another approach is to use tabletop high-order harmonic (HHG) sources [11] for sub-100-nm spatial resolution imaging [12]; however, typical 10 −6 -10 −5 HHG conversion efficiency is very low and often does not allow for a proper reconstruction [13], the system is very complicated, and typical CDI requires time-consuming numerical data processing. Ptychographic schemes, although providing very high spatial resolution, are serial in nature, extensively time-consuming and computationally demanding.…”