Picosecond Soft-X-ray Laser Interferometer for Probing Nanometer Surface Structure

We have developed a soft-X-ray laser interferometer based on a double Lloyd's mirror and obtained a single-shot interferogram using a 7-ps-duration pulse at a wavelength of 13.9 nm. Micrometer grooves with a depth of 5 nm were successfully reconstructed from the interferogram. The lateral and depth resolutions were estimated to be 1.5 µm and better than 1 nm, respectively. This interferometer will be an attractive diagnostic device for observing transiently changing nanometer-scale deviations on solid surfaces.