Phonon Energy Dependent Energy Transfer Upconversion for the Red Emission in the Er³⁺/Yb³⁺ System

Abstract

The red emission through upconversion (UC) upon 980 nm excitation based on Er3+/Yb3+ combination is very attractive for bioimaging applications. The intensity of the red emission is observed to be strongly dependent on the host materials. However, the origin of the behavior and the quantitative dependence remain unclear. Here, the effectiveness of the second step UC excitation from the Er3+ intermediate state 4I13/2 to the 4F9/2 level by energy transfer from Yb3+ is studied for three popular hosts (β-NaYF4, Ba5Gd8Zn4O21, and Y2O3) that have different phonon energies. Their emission efficiencies of the red emitting state are calculated, and the radiative lifetime of the 4F9/2 level in Ba5Gd8Zn4O21 is reported for the first time. We present a spectroscopic method to evaluate the relative energy transfer coefficients for the three hosts and find the coefficient increases markedly with the increase of phonon energy, reflecting the nature of phonon-assisted energy transfer. The coefficient for β-NaYF4 is 89 and 408 times smaller than that for the other two oxide hosts, well revealing the origin of the green emission governed UC in β-NaYF4 and the red emission in the other two. Accordingly, a comprehensive analysis of the luminescence dynamical processes shows that selecting material with appropriate phonon energy is essential for both effective excitation and efficient emission of the red level.

Bi3+-Sensitized La2Zr2O7:Er3+ Transparent Ceramics with Efficient Up/Down-Conversion Luminescence Properties for Photonic Applications

“…To deeply understand the up-conversion mechanism, the excitation power-dependent up-conversion luminescence strength is investigated. The nonlinear function of this dependence can be described as follows where n represents the number of pump photons required to populate the emission states Figure exhibits the slope obtained from fitting the log­( I em ) vs log­( P pump ) plot for LZO:1% Er,2% Bi.…”

Dispersion compensation of optical systems utilizing fiber Bragg grating at 15 Gbits/s

“…Therefore, the amplified signal only along the direction of propagation. The atom when it is 'faded', always transferred its energy at the same level and same direction for the incoming light [16]. As a result, all additional signal strength will be directed to the same position and direction of the incoming signal.…”

Enhancing IR to NIR upconversion emission in Er3+-sensitized phosphors by adding Yb3+ as a highly efficient NIR-emitting center for photovoltaic applications

“…As the Yb 3+ concentration increases in doubly doped samples, the abatement of the rise time reveals that the average lifetime of NIRemitting centers is shortened because of the shorter radiative lifetime of Yb 3+ 2 F 5/2 than that of Er 3+ 4 I 11/2 . 42 It is usually agreed that a small amount of Yb 3+ codoping will hardly affect the lifetime of Er 3+ 4 I 13/2 owing to the similar ionic radii and the characteristics between rare earth elements. Hence, the decay time should be approximately the same in doubly Fig.…”