Laser excitation-induced structure distortion and persistent spectral hole burning of Eu 3+ in BaFCl

Abstract

Persistent spectral hole burning (PSHB) has been demonstrated in the inhomogeneously broadened 7 F 0→ 5 D 0 transition of Eu 3+ ions in crystals of BaFCl at temperatures below 77 K. It was shown that the observed PSHB effect was due to laser excitation-induced site conversion. In the lattice of BaFCl, multiple Eu 3+ sites formed due to charge imbalance and the presence of defects. Eu 3+ population at one site could be depleted and converted to another site. This process was not optically reversible and holes were erased only when temperature was increased to 150 K. Persistent holes burned at 3 K had an average width of 500 MHz while hyperfine transient holes burned at the same temperature were only 25 MHz wide. Although cycling of sample temperature did not affect the shape of the persistent hole, hole width and peak position were quadratic functions of temperature.