Energy level structure and optical dephasing under magnetic field in Er³⁺:LiYF₄ at 1.5 μm

Er3+:LiYF4 is a material where optical inhomogeneous linewidths are smaller than hyperfine splittings, which could be advantageous for quantum information processing protocols. We investigated the Zeeman and hyperfine structures under magnetic field by optical spectroscopy at 1.5 μm and found a good agreement with calculations based on crystal field wavefunctions. Since Zeeman splittings have a non-linear dependance on the magnetic field, this calculations could be useful to estimate energy level structures for arbitrary field strengths and orientations. Coherence lifetimes have been measured on a 100 ppm erbium doped sample under a 2.2 T magnetic field. Values up to 4.7 μs have been observed, with an exponential decay of the echo intensity as a function the pulse delay