Highly efficient near-infrared to visible up-conversion process in NaYF_4:Er~(3+),Yb~(3+)

摘要

Up-conversion (UC) entails the addition of two (or more) photons to generate one of higher energy. This process is very interesting, both from a fundamental point of view as well as for (future) applications. Here, dependence of the emission spectra on excitation power and measurement temperature are reported for the very efficient near-infrared to visible photon UC material NaYF_4: 2% Er~(3+), 18% Yb~(3+). In the high-power limit for continuous-wave laser excitation, roughly 50% of all near-infrared photons absorbed by the material are up-converted and emitted in the visible spectral range. The excitation spectrum shows a 39 cm~(-1) energy gap between the two lowest crystal-field components ∣0> and ∣1> of the Yb~(3+) ~2F_(5/2) multiplet, which sensitizes the UC emission. There is very efficient energy transfer to the lowest energy crystal-field component of the Er~(3+) ~4I_(11/2) state from ~2F_(5/2)∣1>, resulting in an activation energy for all Er~(3+) related up- and down-conversion emissions that scales with the number of excitation photons required multiplied by the 39 cm~1energy gap. frequency conversion; harmonic generation, including higher-order harmonic generation; other nonlinear optical materials; photorefractive and semiconductor materials; optical properties of bulk materials and thin films; photoluminescence, properties and materials