Tailoring the 3F4 level lifetime in Tm3+: Y3Al5O12 by Eu3+ co-doping for signal processing application

Tm3+: Y3Al5O12 (Tm:YAG) crystal is a promising material for high-resolution spectral analysis of broadband radio-frequency (RF) signals, where the absorption spectrum is modified via spectral hole burning. In Tm:YAG, the efficiency of the spectral tailoring is limited by the long-lived metastable level F-3(4), acting as a bottleneck for the optical pumping mechanism. We demonstrate that co-doping Tm:YAG with Eu3+ ions can significantly shorten the optical lifetime of F-3(4) state, while that of H-3(4) is essentially conserved. We show with a model that these modified lifetimes allow faster tailoring of the absorption profile. Because of their low cost and easiness of processing, we use Tm3+ and Eu3+ co-doped Y3Al5O12 ceramics to probe the energy transfer efficiency and find the optimal cation co-doping concentration. Furthermore, we show that Eu3+ co-doping increases the inhomogeneous broadening on the Tm3+ optical transition, hence the spectral analysis bandwidth. Finally, we confirm these results on a single crystal grown by the Czochralski method.