Manipulation of the magnetic dipole and electric dipole emissions by the TiO2:Eu3+ inverse opal photonic crystals

Abstract

The TiO₂:Eu³⁺ inverse opals have the anatase structure and can be analyzed approximately by the two-dimensional photonic crystal. The emission spectra of the Eu³⁺ ions in the TiO₂:Eu³⁺ inverse opal demonstrate that the inverse opal has significant manipulation effect on the emission of the Eu³⁺ ions. With the polystyrene (PS) microsphere size of 300 nm, the emission intensity ratio of the magnetic dipole transition ⁵D₀→⁷F₁ to the electric dipole transition ⁵D₀→⁷F₂ increases by about 4.9 times in the TiO₂:Eu³⁺ inverse opal in comparison with the reference TiO₂:Eu³⁺ nanomaterials sample, meanwhile the electric dipole emission ⁵D₀→⁷F₄ at 695 nm also increases significantly. With the deviation of the PS microsphere size, the above manipulation effect also decreases. The theoretical analysis implies that the above manipulation is mainly due to the forbidden photonic band of the TE mode in the TiO₂:Eu³⁺ inverse opal, which results in the decrease of the electric local density of state in the forbidden photonic band and the decrease of the emission ⁵D₀→⁷F₂, on the contrary, the corresponding emissions ⁵D₀→⁷F₁ and ⁵D₀→⁷F₄ will increase.