Ultra-broadband extreme-ultraviolet lensless imaging of extended complex structures

TL;DR

This paper presents a novel lensless imaging technique using two time-delayed coherent pulses, enabling high-resolution, support-free imaging of complex objects across a broad spectral range, including extreme-ultraviolet wavelengths.

Contribution

The authors introduce a spectrally resolved phase retrieval method that removes spectral bandwidth and support constraints in lensless imaging, applicable to ultra-broadband sources.

Findings

Achieved diffraction-limited imaging with broadband light sources.

Demonstrated imaging of complex objects without support structures.

Validated method with extreme-ultraviolet high-harmonic sources.

Abstract

Lensless imaging is an elegant approach to high-resolution microscopy, which is rapidly gaining popularity in applications where imaging optics are problematic. However, current lensless imaging methods require objects to be placed within a well-defined support structure, while the light source needs to have a narrow, stable, and accurately known spectrum. Here we introduce a general approach to lensless imaging without spectral bandwidth limitations or sample requirements. We use two time-delayed coherent light pulses, and show that scanning the pulse-to-pulse time delay allows the reconstruction of diffraction-limited images for all spectral components in the pulse. Moreover, an iterative phase retrieval algorithm is introduced, which uses these spectrally resolved Fresnel diffraction patterns to obtain high-resolution images of complex extended objects without any support requirements. We demonstrate this two-pulse imaging method with octave-spanning visible light sources (in both transmission and reflection geometries), and with broadband extreme-ultraviolet radiation from a high-harmonic source. This demonstrates that our approach enables effective use of low-flux ultra-broadband sources, such as table-top soft-X-ray systems, for high-resolution imaging.