Scientists at SSRL have demonstrated a novel approach for improving the efficiency of an x-ray microscopy technique that may in particular prove beneficial for imaging radiation-sensitive objects such as biological samples. The findings, published in the October 2006 issue of Applied Physics Letters, should enhance imaging of sensitive samples and improve imaging with future ultra-short pulsed light sources, such as the Linac Coherent Light Source.

Using Fourier Transform Holography (FTH) with 1.58 nm wavelength "soft x-rays," the team of scientists extended the detection limit of high-resolution lensless imaging without increasing radiation exposure. FTH reconstructs a sample's microscopic image from its soft x-ray scattering pattern alone. With this lensless technique, coherent light scattered by a sample interferes with light scattered from a reference aperture to form a hologram. An image of the sample is analytically reconstructed from the hologram using a simple, direct process called a Fourier transformation. By illuminating several references with coherent x-rays, multiple holographic images of the specimen are reconstructed simultaneously.

Holographic references were defined by five nanoscale holes, and the test sample was a 1-mm tall block letter F. Its diffraction pattern was recorded as a hologram on an x-ray sensitive digital camera. The researchers produced a recognizable composite image of the sample after detecting only 2500 x-ray photons. The group found that compiling holographic images from multiple reference sources improves image quality by minimizing noise from imaging systems.

The team of Stanford researchers and their collaborators conducted the proof-of-principle experiment at SSRL beam line 5-2. To learn more about this research see the full scientific highlight at:
http://www-ssrl.slac.stanford.edu/research/highlights_archive/ft-holgraphy.html

W. F. Schlotter, R. Rick, K. Chen, A. Scherz, J. Stöhr, J Lüning, S. Eisebitt, Ch. Günther, W. Eberhardt, O. Hellwig, I. McNulty, "Multiple reference Fourier transform holography with soft x-rays", Applied Physics Letters 89 (16): Art. No. 163112 OCT 16 2006