Holograms, love em’ or hate em’, are everywhere. 3-D images of the Vitruvian Man, the famous da Vinci drawing, and the bacterium Spiroplasma milliferum are even popping up at the Lawrence Berkeley National Laboratory in California and the FLASH free electron laser facility in Hamburg, Germany.
Researchers at the two institutes created the sharpest, most intense X-ray holograms ever made, using new techniques that made the process thousands of times more effective than previous methods. The resolutions for these holograms are the best ever reported.
The X-ray hologram of the Vitruvian Man was less than two square micrometers (millionths of a meter, or microns), engraved with a nanowriter, an ultra-high resolution lithography machine that can generate an electron beam at extremely high energies, with very tiny diameters on the nanometer (billionths of a meter) level. It required a five-second exposure to the beam and had a resolution of 50 nanometers. The Spiroplasma milliferum hologram was made at 150-nanometer resolution and computer refined to 75 nanometers, and required a beam exposure of 15 femtoseconds (quadrillionths of a second).
Holography is a lot like photography, except your camera is a laser and the images produced are in three dimensions. Invented by Hungarian-born physicist Dennis Gabor (who snagged a Nobel Prize for it in 1971), a traditional hologram produces a 3-D image of an object using a reflected laser beam of visible light. Holograms are able to map the intensity of the light reflected by the subject much like regular photography, but can also record information about the interference pattern of the light waves.
In a similar process, X-ray holography uses X-rays instead of visible light. Lasers are essential to making holograms, as they produce coherent (all in the same phase) light. A beam of coherent light is shined through two adjacent holes- one showing the subject to be holographed, and the other a small reference hole. As the light scatters, the two beams combine and become jumbled, forming a 3-D image.
X-rays work better than visible light because they have a shorter wavelength and can therefore illuminate fine details. They are also more powerful, having the ability to penetrate into the nooks and crannies of the subject’s matter and take note of differences in chemical composition.