Study of Erbium-doped yttrium orthovanadate crystal for the microwave to optical transduction*

Quantum transduction between the microwave and optical domain is essential for connecting superconducting quantum platforms in a quantum network. Ensembles of rare-earth ions (REIs) coupled to both optical and microwave cavities offer a promising architecture for achieving this conversion because of their collective and coherent properties in the microwave and optical domains. The critical properties of the REI ensemble needed for high transduction efficiency are the optical and microwave transition dipole moments and the optical and spin inhomogeneities.
Erbium ions are of particular interest because they have transitions at telecom wavelengths which allows for the compatibility with optical fiber telecommunication networks. Here, we report the bulk properties of Erbium-doped yttrium orthovanadate (Er:YVO) including the Zeeman splitting, optical absorption spectra, oscillator strength, and spin inhomogeneity. We also demonstrate proof of concept microwave to optical conversion with a loop gap microwave resonator. The measured strong dipole moment and narrow inhomogeneities point to the Er:YVO as a promising material for quantum transduction.