Pulsed upconversion of Tm3+-doped sol–gel silicate glasses

Upconversion processes allow materials to emit light of shorter wavelength than the light incident upon them. Materials with high upconversion efficiency have numerous potential applications in solid-state physics, such as blue upconversion lasers. We study the time-evolution of upconversion fluorescence of Tm3+ in a sol–gel glass host following pulsed, red light excitation. The 1D2→3F4 intensity varies quadratically with the laser intensity, indicating a two-photon upconversion mechanism. Maximum upconversion intensity occurred for 0.5% Tm3+ with 1% Al3+. We analyzed the main relaxation processes affecting the upconversion emission, namely ion clustering and atmospheric water adsorption.