High Resolution Digital X-Ray Detection via Optical Interrogation of Electro-Optic Materials

We report on the development of a high resolution (greater than 30 lp/mm), high quantum efficiency x-ray detector in the 40 to 60 keV range using non-linear optics. Typical indirect x-ray detectors use a scintillation material to convert high energy x-ray photons into a larger number of lower energy visible photons. Indirect x-ray detectors with the previously stated specifications have a low quantum efficiency due to the combination of a thin scintillation material, which has little x-ray stopping power, and a limited ability of the optical train and CMOS sensor to collect the visible photons. Instead of using a scintillator to convert incident x-rays into lower energy visible photons, we explore the use of non-linear optics to convert incident x-rays into a localized change in the index of refraction, which can be measured with optical interferometry. The non-linear optic consists of a biased Pockels Cell. When x-rays interact with the cell they release space charges which modify the electric field within the cell and thus changes its index. With this new design of x-ray detector, we explore the tradeoffs between x-ray stopping power, transverse spatial resolution, temporal resolution, and signal to noise ratio.