Lensless Diffractive Imaging Using Tabletop Coherent High-Harmonic Soft-X-Ray Beams

We present the first experimental demonstration of lensless diffractive imaging using coherent soft x rays generated by a tabletop soft-x-ray source. A 29 nm high harmonic beam illuminates an object, and the subsequent diffraction is collected on an x-ray CCD camera. High dynamic range diffraction patterns are obtained by taking multiple exposures while blocking small-angle diffraction using beam blocks of varying size. These patterns reconstruct to images with 214 nm resolution. This work demonstrates a practical tabletop lensless microscope that promises to find applications in materials science, nanoscience, and biology.

Figure 1

Experimental setup for lensless imaging using coherent high harmonic beams at a wavelength of 29 nm. A single harmonic order is selected and focused using a pair of normal-incidence multilayer mirrors. The sample stage is positioned near the focus, where it scatters the soft-x-ray beam onto a CCD. Inset: measured logarithmically scaled soft-x-ray beam profile that is a near-Gaussian ${\mathrm{TEM}}_{00}$ over 4 orders of magnitude.

Figure 2

(a) Optical image of $\mathcal{J}$ slit. (b) Oversampled diffraction pattern from this sample where the diffraction at the edge of the image corresponds to a momentum transfer of $0.018{\mathrm{nm}}^{-1}$. (c) Magnitude of the reconstructed lensless image.

Figure 3

(a) SEM image of a masked carbon film; (b) oversampled soft-x-ray diffraction pattern where the diffraction at the edge of the image corresponds to a momentum transfer of $0.059{\mathrm{nm}}^{-1}$; (c) magnitude of the reconstructed lensless image. The correspondence in size, number and position of holes, and aspect ratios between the EUV image and the SEM image can be seen. One pixel in the reconstructed image corresponds to 107 nm. The inset in (c) shows a line scan taken along the direction noted with the green solid line, demonstrating a spatial resolution of 214 nm.