Quadratic Zeeman Spectral Diffusion of Thulium Ion Population in a Yttrium Gallium Garnet Crystal

TL;DR

This paper models and improves spectral hole burning in Tm:YGG crystals, revealing how magnetic fields cause spectral diffusion via the quadratic Zeeman effect, impacting quantum memory applications.

Contribution

It introduces a rate equation model that predicts spectral structures and demonstrates how magnetic fields induce spectral diffusion through the quadratic Zeeman effect in Tm:YGG.

Findings

Good agreement between model and experiments at zero magnetic field

Magnetic field causes spectral diffusion proportional to the quadratic Zeeman effect

Adiabatic hole-burning pulses reduce power-dependent broadening

Abstract

The creation of well understood structures using spectral hole burning is an important task in the use of technologies based on rare earth ion doped crystals. We apply a series of different techniques to model and improve the frequency dependent population change in the atomic level structure of Thulium Yttrium Gallium Garnet (Tm:YGG). In particular we demonstrate that at zero applied magnetic field, numerical solutions to frequency dependent three-level rate equations show good agreement with spectral hole burning results. This allows predicting spectral structures given a specific hole burning sequence, the underpinning spectroscopic material properties, and the relevant laser parameters. This enables us to largely eliminate power dependent hole broadening through the use of adiabatic hole-burning pulses. Though this system of rate equations shows good agreement at zero field, the addition of a magnetic field results in unexpected spectral diffusion proportional to the induced Tm ion magnetic dipole moment and average magnetic field strength, which, through the quadratic Zeeman effect, dominates the optical spectrum over long time scales. Our results allow optimization of the preparation process for spectral structures in a large variety of rare earth ion doped materials for quantum memories and other applications.