Optical decoherence and persistent spectral hole burning in Tm3+:LiNbO3

We report studies of decoherence and spectral hole burning for the 794 nm optical transition of thulium-doped lithium niobate. In addition to transient spectral holes due to the 3H4 and 3F4 excited states of Tm3+, persistent spectral holes with lifetimes of up to minutes were observed when a magnetic field of a few hundred Gauss was applied. The observed anti-hole structure identified the hole burning mechanism as population storage in the 169Tm nuclear hyperfine levels. In addition, the magnetic field was effective in suppressing spectral diffusion, increasing the phase memory lifetime from 11 μs at zero field to 23 μs in a field of 320 Gauss applied along the crystal’s c-axis. Coupling between Tm3+ and the 7Li and 93Nb spins in the host lattice was also observed and a quadrupole shift of 22 kHz was measured for 7Li at 1.7 K. A Stark shift of 18 kHz cm/V was measured for the optical transition with the electric field applied parallel to the c-axis.