Anomalously fast energy transfer between manganese and thulium in fluoride glasses

The laser performance of rare earth doped crystals and glasses can be significantly improved by codoping with an additional ion which absorbs the pump light and efficiently transfers the energy to the lasing rare earth ion. It has been found recently that a fast energy transfer can occur at short times inconsistent with the standard Förster-Dexter model. Such anomalous behaviour may be due to additional mechanisms such as physical pairing of donors and acceptors resulting in additional short-range interactions which increase the transfer rate between donors and acceptors. The models developed are compared to the experimental results of energy transfer between Mn(II) and Tm(III) and Mn(II) and Nd(III) in fluoride glass.