Multi-phonon assisted upconversion emission and power dependence studies in LaF3:Er3+ phosphor

LaF3:Er3+ phosphor is synthesized through chemical precipitation method and its upconversion (UC) emission studies have carried out using 532-nm excitation. Phosphor has shown two-photon absorption UV bands at the 325 nm, 342 nm, 383 nm, 403 nm and 411 nm wavelengths. At relatively higher excitation powers multi-phonon assisted energy migration from 2H11/2 (4S3/2) level to the upper 4F3/2, 4F5/2 and 4F7/2 levels has observed and this energy migration opened new channel of emission at 440 nm, 453 nm and 488 nm due to the 4F3/2 → 4I15/2, 4F5/2 → 4I15/2 and 4F7/2 → 4I15/2 transitions, respectively. Temperature dependent UC measurement is also done and observed emission pattern is correlated with the power dependence studies. Upconversion bands at 411 and 488 nm wavelengths have shown reversal in intensity as either excitation power or sample temperature is increased and hence these two bands are found to act as optical switch. Planck blackbody like continuum emission has also observed at higher excitation powers.

Excitation power dependence of upconversion emission intensity of Er3+ ions in LaF3 phosphor is performed. Phosphor has shown two-photon excited UV/visible UC bands at the 325 nm, 342 nm, 383 nm, 403 nm, 411 nm, 440 nm, 453 nm, 470 nm and 488 nm wavelengths on 532 nm excitation wavelength. At the increased excitation powers multi-phonon assisted energy migration from 2H11/2 (4S3/2) level to the upper 4F3/2, 4F5/2 and 4F7/2 levels has observed which opened up new channels for the emission at 440 nm, 453 nm and 488 nm due to the 4F3/2 → 4I15/2, 4F5/2 → 4I15/2 and 4F7/2 → 4I15/2 transitions, respectively. Planck blackbody like continuum emission has also observed at increased excitation power.Figure optionsDownload as PowerPoint slideHighlights
► Observation of UV bands in LaF3:Er3+ phosphor on 532-nm excitation.
► Multiphonon assisted energy migration from 2H11/2 (4S3/2) level to the upper 4F3/2, 4F5/2 and 4F7/2 levels.
► Reversal in intensity of 411 and 488 nm emission bands with excitation power or the sample temperature.
► Continuum emission at increased excitation powers due to the large multiphonon emissions.