Optical Properties and Upconversion Luminescence of BaTiO(3) Xerogel Structures Doped with Erbium and Ytterbium

Erbium upconversion (UC) photoluminescence (PL) from sol-gel derived barium titanate (BaTiO(3):Er) xerogel structures fabricated on silicon, glass or fused silica substrates has been studied. Under continuous-wave excitation at 980 nm and nanosecond pulsed excitation at 980 and 1540 nm, the fabricated structures demonstrate room temperature PL with several bands at 410, 523, 546, 658, 800 and 830 nm, corresponding to the (2)H(9/2) → (4)I(15/2), (2)H(11/2) → (4)I(15/2), (4)S(3/2) → (4)I(15/2), (4)F(9/2)→ (4)I(15/2) and (4)I(9/2)→ (4)I(15/2) transitions of Er(3+) ions. The intensity of erbium UC PL increases when an additional macroporous layer of strontium titanate is used beneath the BaTiO(3) xerogel layer. It is also enhanced in BaTiO(3) xerogel films codoped with erbium and ytterbium (BaTiO(3):(Er,Yb)). For the latter, a redistribution of the intensity of the PL bands is observed depending on the excitation conditions. A multilayer BaTiO(3):(Er,Yb)/SiO(2) microcavity structure was formed on a fused silica substrate with a cavity mode in the range of 650–680 nm corresponding to one of the UC PL bands of Er(3+) ions. The obtained cavity structure annealed at 450 °C provides tuning of the cavity mode by 10 nm in the temperature range from 20 °C to 130 °C. Photonic application of BaTiO(3) xerogel structures doped with lanthanides is discussed.