24 August 2017 Light output enhancement for a plastic scintillator using nanofibers
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Abstract
Electronic portal imaging devices (EPIDs) are x-ray detector systems conventionally used for medical imaging applications in cancer radiotherapy. Our group has developed a novel prototype EPID with the unique capability of performing both imaging and dose measurements. Our prototype utilizes an array of plastic scintillating fibers in place of the standard copper and gadolinium dioxysulfide phosphor components1.

While our prototype EPID exhibits a detective quantum efficiency that exceeds that of commercial products, there is further scope for improvement. In particular, there is scope to improve optical coupling between the scintillating fiber array and the underlying photodetector where currently an air gap exists. Here, we investigate the effect of a layer of polystyrene nanofibers placed at the end interface of the scintillator array on light extraction efficiency using finite element modelling. We demonstrate that the total light extraction, which depends on the polarization of the incident light, can be enhanced by up to 14%.

This enhancement stems from two effects: Bragg diffraction arising from the periodic arrangement of the fibers and Whispering Gallery Modes (WGMs) formed at each fiber’s cross-section due to Mie resonances. We show that the nanofibers increase optical transmittance above the critical angle. Moreover, we demonstrate that the light extraction efficiency strongly depends on the polarization of the incident light (s- and p-polarizations), as well as the diameter and periodicity of the nanofibers.
Conference Presentation
© (2017) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Zhangkai J. Cheng, Zhangkai J. Cheng, Samuel J. Blake, Samuel J. Blake, Phil Vial, Phil Vial, Ming Lu, Ming Lu, Zdenka Kuncic, Zdenka Kuncic, Shaghik Atakaramians, Shaghik Atakaramians, } "Light output enhancement for a plastic scintillator using nanofibers", Proc. SPIE 10395, Optics and Photonics for Information Processing XI, 103950D (24 August 2017); doi: 10.1117/12.2273531; https://doi.org/10.1117/12.2273531
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