Correlated inhomogeneous absorption profiles across distinct optical transitions in a rare-earth doped crystal

TL;DR

This study reveals spectral correlations between two optical transitions in Er$^{3+}$:YSO crystals, offering new insights into the microscopic origins of inhomogeneous distributions in rare-earth-doped materials.

Contribution

It demonstrates, for the first time, spectral correlations between two optical transitions in a rare-earth-doped crystal using high-resolution spectroscopy and spectral hole burning techniques.

Findings

Spectral correlations exist between the two optical transitions.

Correlations provide insight into local environment distributions.

Results enhance understanding of inhomogeneous broadening mechanisms.

Abstract

In rare-earth ion-doped crystals, inhomogeneous absorption profiles reflect the distribution of local environments experienced by individual ions. While each optical transition probes this distribution differently, their fine spectral structures may retain correlations arising from shared local perturbations. In this paper, we present a low-temperature, high-resolution spectroscopic study in Er$^{3+}$:YSO of the transition $^{4}I_{15/2}$ - $^{4}I_{11/2}$ at 980 nm and compare it to the well-known transition $^{4}I_{15/2}$ - $^{4}I_{13/2}$ at 1.5 $\mu$m. Using spectral hole burning on one transition while monitoring the other, we uncover for the first time spectral correlations between two optical transitions, providing new insight into the microscopic origin of inhomogeneous distributions in rare-earth-doped crystals.