Elementary holographic gratings, that are recorded by visible light in iron-doped photorefractive lithium-niobate crystals, are erased by homogeneous x-ray illumination. The speed of erasure is measured depending on crystal parameters and on the acceleration voltage of the x-ray tube. A simple model is proposed to explain the dependence of the x-ray conductivity on the doping level and oxidation / reduction state. Furthermore, hologram erasure by x-rays is used to build an x-ray imaging system with a high spatial resolution. X-rays yield a conductivity pattern that erases an elementary holographic grating locally. The diffracted visible light now bears the x-ray image. Structures of 25 µm size are easily resolved with a dose of 90 Gray and a signal-to-noise ratio of 6. Such a detector may combine outstanding spatial resolution with the ability to detect hard x-rays without any fading.
© 2003 Optical Society of AmericaPDF Article