Wolfgang Radtke

Sputter Epitaxy Of Iron-Garnet Waveguides

A single-mode asymmetric tri-layer weakly guiding film waveguide made of bismuth-iron garnet has been grown on a (111)(Gd,Ca)3(Ga,Mg,Zr)5O12 substrate by rf magnetron sputtering. The stack consists of an epitaxial core, an epitaxial cladding, and an amorphous absorber layer. The thickness and the refractive index of the three layers, and the absorption coefficient of the absorber layer are optimized in terms of low insertion loss of the fundamental mode but strong dissipation of higher modes. Light propagation measurements at 1.3 µm wavelength show that the fundamental mode is well confined to the core layer while the higher modes, extending over the whole stack, are suppressed by at least 29.5 dB. These data are confirmed by theoretical predictions.