Spectroscopic investigations of a Ti:Tm:LiNbO3 waveguide for photon-echo quantum memory

We report the fabrication and characterization of a Ti4+ : Tm3+ : LiNbO3 optical waveguide in view of photon-echo quantum memory applications. Specifically, we investigated room- and cryogenic-temperature properties of the waveguide, and the Tm3+ ions, via absorption, spectral hole burning, photon echo, and Stark spectroscopy. For the Tm3+ ions, we found radiative lifetimes of 82 mu s and 2.4 ms for the H-3(4) and F-3(4) levels, respectively, and a 44% branching ratio from the H-3(4) to the F-3(4) level. We also measured an optical coherence time of 1.6 ss for the H-3(6) <-> H-3(4), 795 nm wavelength transition, and investigated the limitation of spectral diffusion to spectral hole burning. Upon application of magnetic fields of a few hundred Gauss, we observed persistent spectral holes with lifetimes up to seconds. Furthermore, we measured a linear Stark shift of 25 kHz cm/V. Our results are promising for integrated, electro-optical, waveguide quantum memory for photons. (c) 2009 Elsevier B.V. All rights reserved.