Ultra-narrow optical inhomogeneous linewidth in a stoichiometric rare earth crystal

Understand

We have obtained a low optical inhomogeneous linewidth of 25 MHz in the stoichiometric rare earth crystal EuCl3 .6H2 O by isotopically purifying the crystal in 35 Cl.

• With this linewidth, an important limit for stoichiometric rare earth crystals is surpassed: the hyperfine structure of 153Eu is spectrally resolved, allowing the whole population of 153Eu3+ ions to be prepared in the same hyperfine state using hole burning techniques.
• This material also has a very high optical density and can have long coherence times when deuterated.
• This combination of properties offers new prospects for quantum information applications.