Ultraslow optical dephasing in Eu3+:Y2SiO5

Abstract

We report the measurement of what we believe to be the narrowest known optical resonance in a solid. This was made on the 7F0→5D0 transition of Eu3+:Y2SiO5 at 1.4 K using photon echoes with sufficiently low laser power to almost eliminate contributions from instantaneous diffusion. The optical resonance widths measured for Eu3+ ions in the two crystallographic sites of Y2SiO5 and in a magnetic field of 100 G are 122 Hz (site 1) and 167 Hz (site 2). These widths are dominated by population decay, but up to 20 Hz is attributed to Y89 spin fluctuations which have been reduced by the applied magnetic field. © 1994 The American Physical Society.