Optimizing Optical Nanostructures for X-ray Detection

Scintillators are vital to X-ray and high-energy particle detection. Specifically, thin scintillators like phosphor screens are a prime component in detectors of soft-X-rays, electron cameras, and light intensifiers. All such applications are limited by the scintillator's response time and efficiency. Moreover, there exists an intrinsic trade-off due to the isotropic nature of spontaneous emission at the heart of the scintillation process: On the one hand, the thicker scintillator layers that are required for high efficiency of detecting the radiation also cause a dramatic image deterioration and blurring. On the other hand, thinner scintillator layers can provide higher image resolution yet that comes at the price of lower efficiency of detecting the radiation and thus a lower signal-to-noise ratio. In this paper, we introduce a novel design of thin scintillators that can achieve simultaneously high-efficiency and high-resolution, by proposing a new concept of scintillating nanophotonic structures. We exploit the photonic local-density-of-states (LDOS) in scintillating nanostructures made from scintillator layers, stacked between other dielectric layers. We use a specialized optimization algorithm to determine the thicknesses of each layer in the multi-layer structure and to maximize the emission rate, directionality, and efficiency. As an example, we examine an overall structure width of only 2.5 mu m, and find that the emission rate can be enhanced by a factor of 5.2 (when combining a scintillator with a refractive index of 1.59 with a dielectric material with a refractive index of 2.1). We show how the optimized structure can enhance the emission in the desired bandwidth to match with any scintillator material, thus improving the detector resolution and efficiency simultaneously in several radiation detection applications.