Optical Waveguide of Nd-Doped Garnet Thin Film RF-Sputtered on Y3Al5O12 Substrate

Abstract
Nd-doped garnet thin-film waveguides which can be used as optical amplifiers were prepared on YAG substrates by rf sputtering. The composition, crystal property and optical propagation loss of the films were found to be quite sensitive to the substrate temperature (T s). The film prepared at T s=650°C was amorphous with a stoichiometric composition Y3Ga5O12, while that prepared at T s=790°C showed a single-crystalline phase and the composition was represented by Y4Ga4O12 with the garnet structure. The propagation loss of light at λ=0.633 µm abruptly decreased from about 30 dB/cm to 5 dB/cm as T s exceeded 700°C. Recrystallized thin films with the stoichiometric composition Y3Ga5O12 were prepared by thermal treatment, and the loss was reduced to about 2 dB/cm.

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