Epitaxial Nd-doped alpha-(Al_1-xGa_x)₂O₃ films on sapphire for solid state waveguide lasers, R. Kumaran, T. Tiedje, S. E. Webster, S. Penson, Optics Lett. 35, 3793-3795 (2010)

Single-crystal aluminum-gallium oxide films have been grown by molecular beam epitaxy in the corundum phase. Films of the (Al_1-xGa_x)₂O₃ alloys doped with neodymium have favorable properties for solid-state waveguide lasers, including a high-thermal-conductivity sapphire substrate and a dominant emission peak in the 1090-1096 nm wavelength range. The peak position is linearly correlated to the unit cell volume, which is dependent on film composition and stress. Varying the Ga-Al alloy composition during growth will enable the fabrication of graded-index layers for tunable lasing wavelengths and low scattering losses at the interfaces.