Abstract
Element-specific contrast enhancement in tabletop coherent diffractive imaging (CDI) is demonstrated by employing an ultrafast extreme ultraviolet (XUV) light source with tunable photon energy. By combining two measurements performed at energies below and above the Al L(2,3) absorption edge, the spatial autocorrelation function of a micron-scale double pinhole in a 300 nm thick aluminum foil is retrieved despite a dominant background signal from directly transmitted light across the entire range of detectable diffraction angles. The fringe visibility in the diffraction patterns is 0 below the Al L(2,3) edge, 0.53 ± 0.06 above the edge, and 0.73 ± 0.08 in the differential image that combines the two measurements. The proof-of-principle experiment demonstrates that the variations of XUV optical constants in the vicinity of an inner-shell absorption edge can be utilized to improve the chemical sensitivity and image reconstruction quality of laboratory-based ultrafast imaging experiments.
Highlights
Microscopy is one of the most fundamental tools to study the structure of matter and to understand the relationship between structural properties and function
Despite the lack of direct phase information in the recorded intensities, real-space images can be reconstructed by combining spatial oversampling of the diffraction patterns with iterative phase retrieval algorithms
The advantage of the method is demonstrated by extracting the spatial autocorrelation function of a micron-scale double pinhole in a 300 nm thick aluminum foil
Summary
Microscopy is one of the most fundamental tools to study the structure of matter and to understand the relationship between structural properties and function. Femtosecond HHG light sources have been employed by the groups of Kapteyn and Murnane [13,14], Miao [15] and Merdji [16,17] to perform multi- and single-shot CDI studies These experiments beautifully demonstrate faithful real-space image reconstructions with up to near diffraction limited spatial resolution. The advantage of the method is demonstrated by extracting the spatial autocorrelation function of a micron-scale double pinhole in a 300 nm thick aluminum foil We envision that this proof-of-principle experiment opens new possibilities for ultrafast imaging applications by enabling chemical contrast and enhancing the reliability of image. Received 27 Aug 2012; revised 19 Oct 2012; accepted 21 Oct 2012; published 5 Nov 2012 19 November 2012 / Vol 20, No 24 / OPTICS EXPRESS 26169 reconstruction algorithms in challenging situations where only a small fraction of the incoming light is scattered by the sample features of interest
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