Ultra fast holography with 32.5nm soft X-rays from FLASH, Hamburg

Dr. H. Chapman (Lawrence Livermore National Laboratory, USA) and his colleagues recently published their new imaging technique, which is a new type of X-ray holography, and some successful data obtained at the free electron laser source, FLASH, Hamburg, Germany. Their technique employs soft X-ray laser pulses which pass through a small hole in a detector mirror, and then encounter a thin, translucent membrane that has been covered with a sample material (140 nm-diameter polystyrene balls) lying just in front of a backing mirror. In the present case, the X-ray pulse is shorter than the time spent traveling through the sample to the backing mirror and then returning. The sample is exploded by extremely strong X-ray photons and its size changes in the brief interval that the pulse takes to reflect back. The time it takes the pulse to return is encoded in the fringe pattern of the X-ray hologram, and this can be read out from the hologram to an accuracy of about one femtosecond. The spatial resolution is 50 nm in this experiment, but this will be further improved by shorter wavelength laser pulses. Their newly developed method opens up new opportunities for structure sciences based on holography, interferometry or coherent diffraction, as well as for studies that investigate the femtosecond dynamics of matter in new ways. It is interesting that the scientists were inspired by Isaac Newton, who noticed in the 18th century that sunlight produced "strange and surprising" light and dark bands on a screen after he had bounced it off a mirror speckled with dust particles. For more information, see the paper, "Femtosecond time-delay X-ray holography ", H. N. Chapman et al., Nature,. 448, 676-679 (2007).