Long-ranged surface plasmon polaritons and their coupling with upconversion emissions in indium-tin-oxide-coated erbium and iron codoped LiNbO3

Abstract

Long-ranged surface plasmon polaritons (SPPs) and their coupling with upconversion emissions (UCEs) were studied in indium tin oxide (ITO)-coated erbium and iron codoped L i N b O 3 (Er,Fe:LN). In this work, ITO is coated on Er,Fe:LN grains to form a noble-metal-like modified ITO layer, namely, a two-dimensional electron gas layer. By meeting phase-matching conditions, SPPs with a definite wave vector can be excited most efficiently. By calculating the attenuated total reflection spectra of the sandwich structure of unmodified ITO/modified ITO layer/LN, the propagation length of SPP can reach as long as 2.0 cm due to the subnanometer ITO modified layer. Experimentally, the location of missing spectral lines in the diffraction pattern and a valley in the transmission spectra are consistent well with the calculations of the phase-matching condition, both serving as valid proofs for SPP excitation. In the ITO-coated Er,Fe:LN grains, a sharp dropping-down process was observed in the UCE’s dynamics, indicating high coupling efficiency from UCEs to SPPs. This work advances the fundamental understanding in electrostatic modification of transparent oxides into visible nonmetal plasmonic materials by simply neighboring to ferroelectric oxides and leads a way toward designing and implementing shortwave plasmonic devices, apart from conventionally used lossy metal constituents.