High resolution transient and permanent spectral hole burning in Ce$^{3+}$:Y$_2$SiO$_5$ at liquid helium temperatures

TL;DR

This study demonstrates high-resolution spectral hole burning in Ce$^{3+}$:Y$_2$SiO$_5$ at 2K, revealing near lifetime-limited linewidths and a slow permanent hole burning process involving trapping via the 5d-state.

Contribution

It provides the first detailed measurements of spectral hole widths, spin relaxation times, and permanent hole burning mechanisms in Ce$^{3+}$:Y$_2$SiO$_5$ at cryogenic temperatures.

Findings

Spectral holes as narrow as 6 MHz were observed.

Homogeneous linewidth is close to the lifetime limit at 3 MHz.

Permanent hole burning reduces fluorescence by over 50% within minutes.

Abstract

We perform hole burning with a low drift stabilized laser within the zero phonon line of the 4f-5d transition in Ce$^{3+}$:Y$_2$SiO$_5$ at 2K. The narrowest spectral holes appear for small applied magnetic fields and are $6\pm4$ MHz wide (FWHM). This puts an upper bound on the homogeneous linewidth of the transition to $3\pm2$ MHz, which is close to lifetime limited. The spin level relaxation time is measured to $72\pm21$ ms with a magnetic field of 10 mT. A slow permanent hole burning mechanism is observed. If the excitation frequency is not changed the fluorescence intensity is reduced by more than 50$\%$ after a couple of minutes of continuous excitation. The spectral hole created by the permanent hole burning has a width in the tens of MHz range, which indicates that a trapping mechanism occurs via the 5d-state.