Optical dephasing by disorder modes in yttrium orthosilicate (Y2SiO5) doped with Eu3+

Anomalous crystals of Eu3+-doped Y2SiO5 (YSO) have been identified where excess dephasing is observed on the 7F0↔5D0 transition at 579.88 nm, in the temperature range 1.4–5 K. This dephasing is attributed to disorder modes due to as yet unidentified structural differences in those crystals compared to normal crystals grown by nominally the same Czochralski method. The excess dephasing amounts to about 500 Hz at 1.4 K, and it shows a linear temperature dependence in the range 1.4–5 K. Above 5 K the temperature dependence is dominated by a T7 behavior associated with the Raman scattering of phonons in a normal crystal.