Wavelength-dependent cross section for optically stimulated luminescence in Y2SiO5:Ce

Abstract

Long-lived defect states in large-band-gap materials can potentially store energy from ionising radiation allowing the materials to be used as dosimeters. The population in many of these dosimetric traps can be read out with optically stimulated luminescence (OSL). OSL is associated with a cross section for the excitation probability, and the wavelength dependence of the cross section provides insight into the physical characteristics of the traps and allows for an optimised readout of OSL-dosimeters.

This paper suggests a novel approach to measuring the optical cross section using a pulsed tunable laser. A model of the evolution of the trap population is used to analyse data taken pulse-by-pulse to determine the cross sections in Y${}_2$SiO₅:Ce. The cross sections are compared to theoretical models in order to determine the trap depth and phonon contribution. The wavelength-dependent cross section increases monotonically as the wavelength decreases, varying by more than two orders of magnitude from $10^{-24}$ at the longest wavelengths (800 nm) to more than $10^{-22}$ m${}^2$ in the green and blue part of the spectrum. Depending on the theoretical model used, the main trap depth is within the range 2.1–2.6 eV with a characteristic value of 2.3 eV, aligning with published results. Additionally, a notable phonon contribution is found with a magnitude that is consistent with previously reported phonon energies.