Formation of Erbium Doped Lithium Niobate Single Crystal in Glass via Femtosecond Laser Irradiation

The formation of single crystals via femtosecond laser in 3D allows for the fabrication of more complex photonic packages and a higher number of optical elements in a single glass substrate. We have previously found a particular glass composition and growth parameters of laser power, scanning rate, and sample temperature that yield single crystal lithium niobate. A characteristic property of these laser written crystals is lattice rotation, a phenomenon of organized defects induced by stresses during the growth process. The challenges in finding sets of parameters yielding single crystal formation and in characterization are discussed, and their effect on the spectral properties of an erbium dopant is explored as various growth parameters are tuned. Engineering the spectral properties of doped laser written crystals has impacts on the fabrication of waveguide lasers and quantum memory applications.