Lasing of Nd3+ in sapphire

We present a rare‐earth‐doped sapphire laser. Single‐crystalline α‐Al2O3 films doped with trivalent neodymium have been grown by pulsed laser deposition on undoped sapphire substrates. The Nd3+ doping concentrations of the films have been varied between 0.3 at.% and 2 at.%. Epitaxial growth was proven by structural and optical characterization of the films. The samples exhibit strongly polarization dependent emission transitions from the 4F3/2 manifold with a fluorescence lifetime of 108 μs and peak emission cross sections of 1.1 × 10−18 cm2 around 1100 nm. Lasing at 1096.5 nm was achieved under Ti:sapphire‐pumping in a planar waveguide configuration with a maximum cw output power of 137 mW and a slope efficiency of 7.5% with respect to the incident pump power. Single crystalline Nd3+:sapphire films were grown with pulsed laser deposition. Fluorescence measurements were performed at room temperature and cryogenic temperatures. A positive refractive index difference of the films with respect to the undoped sapphire substrate enabled waveguiding. Laser oscillation was achieved in planar waveguide configuration with a maximum cw output power of 137 mW, slope efficiency of 7.5% and a threshold of 96 mW with respect to incident pump power.