Cambridge 7th to 9th September
Presenting Author:
Cyril Koughia
<cyril.koughia@usask.ca>
article posted 3 May 2015
Cyril Koughia
======
The influence of radiation diffusion (radiation trapping)
on spectra and measured lifetimes of
4F9/2 -4I115/2, 4I9/2 -4I15/2, 4I11/2 -4I15/2 and 4I13/2 -4I15/2
emission bands in GeGaS glasses doped with erbium
Cyril Koughia* and Safa Kasap
Department of Electrical and Computer Engineering, University of Saskatchewan.
Behind the effect of radiation diffusion (RD), also known as radiation trapping, is a series the sequential emissions and absorptions of radiation by participating atoms or ions. The RD was first observed in mercury vapors and received its name due to the similarity of mathematical descriptions of RD and regular diffusion [1]. The origin of RD is a strong spectral overlap of emission and absorption bands. Nowadays, this effect is widely observed in glasses doped with Er3+ ions where there is a significant spectral overlap (as seen in Fig.1(d) and (h)) of 4I13/2 -4I15/2 absorbing and emissive interband transitions. This effect, also called "self-absorption", is known to be responsible for remarkably different characteristics of photoluminescence (PL) in bulk and powdered materials such as PL decay rate and PL spectra [2,3,4].
It is worth noting that all above mentioned results refer to 4I13/2 and 4I15/2 manifolds. However, Fig.1(a) - (h) show that significant spectral overlap may be observed also for other optical transitions involving 4I11/2, 4I9/2 and 4F9/2 manifolds leading to significant differences between PL spectra and decay rates for bulk and powdered materials (Fig.1(e) - (l)). In present paper we discuss the observed experimental data and report a Monte-Carlo model that allows us to simulate the observed effects of RD in 4F9/2 -4I115/2, 4I9/2 -4I15/2, and 4I11/2 -4I15/2 emission/absorption bands.
References:
1. E.A. Milne, J. London Math. Soc. 1, 40-51 (1926)
2. F. Auzel, F. Bonfigli, S. Cagliari, G. Baldacchini, J. Luminescence, 94-95 (2001) 293-297.
3. M. Mattarelli, M. Montagna, L. Zampedri, A. Chiasera, M. Ferrari, G. C. Righini, L. M. Fortes, M. C. Gonçalves, L. F. Santos, R. M. Almeida, Europhys. Letter. 71 (2005) 394-399.
4. C. Koughia, S. O. Kasap, Optics Express16 (2008) 7709-7714.