Modification of the Near-Infrared Spontaneous Emission in Er3+-Activated Inverse Silica Opals

Ordered SiO2:Er3+ inverse opal films are fabricated by sol-gel technique in combination with a self-assembly method to examine their potential as a suitable platform to tailor the spontaneous emission lifetime of Er3+ ions and its concentration quenching (CQ). Good ordering on long-range scale is evidenced by means of scanning electron microscopy, whereas reflectance measurements display a green bright color, as it results from optical Bragg diffraction from the (111) crystal planes. Moreover, it is observed that the spontaneous decay rates (SDRs) of the inverse opals are suppressed, in contrast to the corresponding reference samples, due to the modulation of the effective refractive index (n(eff)), in agreement with the virtual cavity model. At the same time, the reduced CQ of Er3+ is attributed to the periodic empty cavity of the inverse opals. These results demonstrate that inverse opals can provide a tool for the enhancement of near-infrared (NIR) luminescence.