Single-shot table-top coherent X-ray imaging with diffraction-limited resolution by nonlinear phase variations

We demonstrated single-shot high-numerical-aperture coherent diffraction imaging (CDI) with a diffraction-limited resolution using table-top X-ray laser at 13.9 nm. In order to achieve the diffraction-limited resolution, a nonlinear phase variation was introduced in a sample so that an asymmetric diffraction pattern with clear visibility could be extended to high spatial frequencies. From the diffraction signal, the sample image was successfully reconstructed with a resolution of 22 nm, which is close to the diffraction-limited resolution of 21 nm, using the phase retrieval procedure. The model calculation and simulations, performed to verify the experimental results, showed that the implementation of the nonlinear phase variation in the sample enhanced the resolution by a factor of about two, as compared to the case of a pure absorption sample. In addition, we examined the CDI with phase controllers introducing nonlinear phase variation illuminated by a table-top femtosecond Kr X-ray laser pulse at 32.8 nm that produced an asymmetric diffraction pattern extended to high spatial frequencies.