Abstract
Radiation trapping (RT) is a phenomenon wherein photons are emitted, absorbed and re-emitted many times before they leave the volume of the material. Trivalent Er3+ ions are particularly prone to RT because there is a whole set of strongly overlapping emission and absorption bands including 4I13/2−4I15/2 and 4I11/2−4I15/2 bands. The effect of RT on the PL decay time was investigated experimentally in this work in a variety of Er3+-doped GeGaS, GeGaSe, GaLaS(O) glasses. Sample geometry (powders, plates, disks, cylinders) and size were varied and the samples were also immersed in glycol, a liquid with high refractive index. PL decay times were measured and compared with the Judd-Ofelt results. A simple model of RT was developed and applied to the above mentioned bands. By comparing model conclusions with experimental data for different sample sizes, we were able to separate the direct relaxation of the 4I11/2 state to ground 4I15/2 state and relaxation via the intermediate 4I13/2 state; and hence obtain an approximate nonradiative lifetime.
Highlights
Radiation trapping (RT) is a phenomenon wherein photons are emitted, absorbed and re-emitted many times before they leave the volume of the material
RT has been observed and reported in a variety of materials where there is a strong overlap of the emission and absorption bands
Eq (3) by (5) we find the ratio of two characteristic PL decay times in powdered and bulk materials as τ(0) τ(L)
Summary
Radiation trapping (RT) is a phenomenon wherein photons are emitted, absorbed and re-emitted many times before they leave the volume of the material. RT has been observed and reported in a variety of materials where there is a strong overlap of the emission and absorption bands. Over the last two decades it has been widely observed in materials doped with multivalent rare earth ions [3,4,5,6,7,8,9,10,11,12,13]. Among various rare earths ions, the trivalent Er3+ offers a unique opportunity for RT because there is a whole set of perfectly overlapping emission and absorption bands [14]. Researchers try to eliminate RT by experimenting on fine powders [7,11] or by using excitation and detection through spatially separated pinholes [15,16,17] or by using a confocal setup [18]
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