The modification of upconversion emissions by photonic band gap in β-NaYF4: Yb3+, Tm3+ inverse opal structures

Abstract

Inverse opal photonic crystals (IOPCs) of β-NaYF4: Yb3+, Tm3+ with various photonic band gap (PBG) are prepared by the sol-gel method with polystyrene (PS) template technique. The modification of upconversion emissions is observed in IOPCs, where the near ultraviolet and blue emissions of Tm3+ ions are simultaneously suppressed and enhanced corresponding to the center and edge of PBG. Also they are alternately suppressed or enhanced resulting from the location change of the PBG. This is mainly attributed to the depression or enhancement effects occurring at the center or the edges of PBG, respectively. Moreover, the branch ratios and the excitation state processes involving suppressed transitions are modified by the increasing population on initial levels of suppressed transitions.