Soft X-ray spectromicroscopy using ptychography with randomly phased illumination

Ptychographic methods can retrieve the complex sample transmittance from diffraction patterns that may have a large dynamic range. For soft X-ray spectromicroscopy, Maiden et al . use a diffuser to randomize the probe phase, reducing the dynamic range of the diffraction data by an order of magnitude. Ptychography is a form of scanning diffractive imaging that can successfully retrieve the modulus and phase of both the sample transmission function and the illuminating probe. An experimental difficulty commonly encountered in diffractive imaging is the large dynamic range of the diffraction data. Here we report a novel ptychographic experiment using a randomly phased X-ray probe to considerably reduce the dynamic range of the recorded diffraction patterns. Images can be reconstructed reliably and robustly from this setup, even when scatter from the specimen is weak. A series of ptychographic reconstructions at X-ray energies around the L absorption edge of iron demonstrates the advantages of this method for soft X-ray spectromicroscopy, which can readily provide chemical sensitivity without the need for optical refocusing. In particular, the phase signal is in perfect registration with the modulus signal and provides complementary information that can be more sensitive to changes in the local chemical environment.