Fig. 1. Flow diagram for the multiwavelength phase retrieval. This method simultaneously reconstructs images for each wavelength.

Fig. 2. Experimental setup for EUV CDI. (a) Schematic of the light path of CDI using an HHG source. (b) The measured spectrum contains three harmonics of 34.3, 39.6, and 46.8 nm. (c) The diffraction intensity of the beam. Scalar bar: 1.25 mm.

Fig. 3. EUV experimental validation using an HHG source. (a) A microscopic photo of the test sample, which was prepared using a two-photon polymerization 3D printing technique. (b) The multiwavelength diffraction pattern shown in log scale. Reconstructed amplitude of the sample, where (c)–(e) are reconstructed results using the traditional mw-CDI, and (f)–(h) are reconstructed results using our proposed algorithm with the combination algorithm of ER, HIO, and DM for different harmonics: (c), (f) 34.3, (d), (g) 39.6, and (e), (h) 46.8 nm. Scalar bar: 7 µm.

Fig. 4. Simulation of EUV mw-CDI imaging for a mixture of Mg and Al. (a) The dual wavelength diffraction pattern is shown in log scale. (b) The refractive index and (c) the extinction coefficient for Mg and Al versus wavelength. (d), (e) Amplitude of the sample used in the simulation at 23.95 and 25.12 nm. (f), (g) Reconstruction results, which match the simulated sample distribution well.