Spectroscopic Investigations of Multiple Environments in Er:CaWO4 through Charge Imbalance

TL;DR

This study uses spectroscopic techniques to analyze multiple local environments of Erbium ions in CaWO4 crystals, revealing detailed energy levels, transition properties, and relaxation behaviors without co-dopants.

Contribution

It provides a comprehensive assignment of energy sublevels and transition characteristics for Er:CaWO4, highlighting multiple environments and their spectroscopic signatures.

Findings

Multiple Erbium environments identified in CaWO4

Complete energy level assignments for key multiplets

Differences in relaxation paths and transition properties

Abstract

We present a detailed spectroscopic study of the $^4\mathrm{I}_{13/2}$ and $^4\mathrm{I}_{15/2}$ Er$^{3+}$ multiplets of Er:CaWO$_4$ grown without a co-dopant. Using photoluminescence and photoluminescence excitation measurements, we find multiple environments into which the Erbium ions are incorporated in the crystal. For the four most prevalent environments, we provide a complete assignment of the $^4\mathrm{I}_{13/2}$ and $^4\mathrm{I}_{15/2}$ sublevel energies. Polarization-dependent absorption and emission spectroscopy allow us to identify the irreducible representations of the states and determine the dipole nature of transitions. In addition, we compare the different relaxation paths within $^4\mathrm{I}_{13/2}$ and $^4\mathrm{I}_{15/2}$ multiplets via line broadening and lifetime measurements. Finally, spectral, lifetime, and polarization measurements indicate similarities between the studied environments.