Nanoscale Ptychography Using Compact Broadband EUV and Soft X-Ray Sources

High-resolution imaging in the EUV and soft X-ray regions holds great promise for applications in microbiology, nanodevice metrology, and materials science. In recent years, ultra-stable coherent EUV and soft X-ray sources based on high-order harmonic generation (HHG) from ultrafast lasers have advanced considerably. These sources enable high-resolution coherent diffractive imaging (CDI), including ptychography, outside of large-scale research facilities. However, HHG radiation is intrinsically broadband, exhibiting either a comb-like structure or a broadband continuum. This is at odds with the temporal coherence requirements of CDI, and thus only a narrow bandwidth is typically selected, leaving most generated photons unused. In our work, we demonstrate high-resolution imaging with a bandwidth of up to 10% at the technologically relevant wavelength of 13.5 nm, representing the broadest spectrum employed to date in EUV ptychography. This progress was made possible by a home-built, ultra-high stability laser and an EUV optical design that enables sub-micrometer spot sizes. Looking ahead, these results will be leveraged to extend ptychographic imaging into the soft X-ray regime, where HHG sources provide lower photon flux, which may be compensated by employing broader bandwidths.