Significant Suppression of Spontaneous Emission in SiO2 Photonic Crystals Made with Tb3+-Doped LaF3 Nanoparticles

SiO 2 inverse opals made with LaF 3:Tb 3+ nanoparticles were fabricated. The spontaneous emission lifetime of the 5 D 4 → 7 F 4 transition of Tb 3+ ions at 542 nm embedded in the SiO 2 inverse opal structure was determined. In contrast to an average lifetime of 2.8 ms in photonic crystals when the photoluminescence of the Tb 3+ envelop was located outside the photonic stop band, a lifetime of 4.0 ms was observed when the Tb 3+ photoluminescence fully overlaps with the photonic stop band in the inverse opal. The obtained results demonstrate that the photonic structure affects the spontaneous emission significantly, resulting in a 40% increase of the luminescence lifetime of Tb 3+ ions. In other words, the density of optical states is reduced at the emission frequency of Tb 3+ (i.e., 542 nm) which reduces the radiative rate constant.