Abstract
A (Lu,Y)2SiO5:Ce (LYSO) crystal, as a heavy inorganic scintillator, is currently in high demand for various applications in the fields of particle detection. However, its high refractive index (n = 1.83) gives restriction on the measurements of rare events or weak particle flow, where high energy resolution is urgently required for detectors based on the crystal. Utilizing the electron beam lithography technique and the ion beam lithography method, we have successfully prepared a 2.0 × 2.0 mm2 large area two-dimensional photonic crystal (PhC) structure on the LYSO crystal surface. Compared with the plain reference sample, the optical measurements show a 53% enhancement of light extraction for the LYSO nanostructured surface, and the resulted improvement of energy resolution (full width at half maximum) is measured to be 43.8% by gaussian fittings to the energy spectra excited by the 241Am α source. With the advantage of high-resolution patterning, high thermal stability, and firm stickiness on the substrate, the present prescription of the PhC fabrication is still favorable for some special fields (e.g., homeland security and space exploration) though the writing process is extremely time consuming and expensive to use.
Highlights
A heavy inorganic scintillator with a prominent characteristic of high internal quantum efficiency (∼40 000 photons/MeV)1 is currently in high demand for various applications such as homeland security, nuclear particle detection,2,3 and medical imaging systems.4,5 both the energy and time resolution, two key properties for those scintillator based detection systems, are always seriously constrained by the low light extraction efficiency on the scintillator-ambient interface that is coupled to the downstream photodetectors
We show a large improvement of energy resolution for LYSO by introducing the photonic crystal (PhC) when a period array of nano-scale holes is etched by electron beam lithography (EBL)
The conversion of pulse amplitude from the PMT to a digit number was performed with the help of an electronic instrument DT5730B (CAEN) and the program, namely, wavedump, on the personal computer (PC)
Summary
A heavy inorganic scintillator with a prominent characteristic of high internal quantum efficiency (∼40 000 photons/MeV) is currently in high demand for various applications such as homeland security, nuclear particle detection, and medical imaging systems. both the energy and time resolution, two key properties for those scintillator based detection systems, are always seriously constrained by the low light extraction efficiency on the scintillator-ambient interface that is coupled to the downstream photodetectors. A heavy inorganic scintillator with a prominent characteristic of high internal quantum efficiency (∼40 000 photons/MeV) is currently in high demand for various applications such as homeland security, nuclear particle detection, and medical imaging systems.4,5 Both the energy and time resolution, two key properties for those scintillator based detection systems, are always seriously constrained by the low light extraction efficiency on the scintillator-ambient interface that is coupled to the downstream photodetectors. According to the conservation of the length of light in-plane k vector k//, only light generated in the scintillator crystals with an in-plane k vector smaller than k0nsci sin θc = nambk0 can radiate into the ambient medium, where k0 is the vacuum vector and nsci and namb are the refraction index of the scintillator and ambient material, respectively.6 This means that a large fraction of light emitted with an angle larger than the critical angle θc is trapped inside the crystals.
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