London, August 2 : An international team of U.S. and German researchers has produced two of the brightest and sharpest x-ray holograms of microscopic objects ever made, with the help of an approach they claim is thousands of times more efficient than previous x-ray-holographic methods.
This advancement is a result of the efforts of experts associated with the Advanced Light Source (ALS) at the U.S. Department of Energy's Lawrence Berkeley National Laboratory, and at FLASH, the free-electron laser in Hamburg.
The researchers have revealed that their approach is inspired by the pinhole camera, a technique known since ancient times.
"Our purpose was to explore methods of making images of nanoscale objects on the time scale of atomic motions, a length and time regime that promises to become accessible with advances in free-electron lasers," says Stefano Marchesini of the ALS, who led the research.
"The technique we used is called massively parallel x-ray Fourier-transform holography, with 'coded apertures.' What inspired me to try this approach was the pinhole camera," the researchers add.
The x-ray hologram made at ALS was of Leonardo da Vinci's famous drawing 'Vitruvian Man', a lithographic reproduction less than two micrometers square, etched with an electron-beam nanowriter.
According to the researchers, the hologram required a five-second exposure, and had a resolution of 50 nanometres.
The hologram made at FLASH was of a single bacterium called Spiroplasma milliferum, which was made at 150-nanometer resolution, and computer-refined to 75 nanometers.
It, however, required an exposure to the beam of just 15 femtoseconds.
The values for the two holograms are among the best ever reported for micron-sized objects.
The researchers believe that technologies already established may help push resolutions they have obtained to only a few nanometres, or even better by using computer refinement.
"Imaging with coherent x-rays will be a key technique for developing nanoscience and nanotechnology, and massively parallel holography will be an enabling tool in this quest," write the researchers in their Nature Photonics article.