Birefringence and Optical Waveguiding Losses in Preferentially $c$-Axis Oriented LiNbO3 Thin Films on SiO2 Produced by Electron Cyclotron Resonance Plasma Sputtering
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LiNbO3 (LN) films deposited on SiO2 substrate by electron cyclotron resonance plasma sputtering and thermal treatment were structurally and optically characterized. Birefringence between 60 and 70% for single crystal was confirmed for $c$-axis oriented films on both Si and SiO2, whereas non-annealed amorphous film was optically isotropic. Crystallization during sputtering produced less than a 10% volume fraction of $c$-axis oriented spherical domains associated with the interface roughness layer. This sample had a large propagation loss of 32 dB/cm at 632.8 nm due to light scattering at the grain boundaries. LN films subjected to solid phase crystallization in a vacuum produced highly $c$-axis oriented columnar texture domains, which yielded propagation losses between 5 and 19 dB/cm, depending on the thickness (0.64–1.35 μm) and the mode order. The bulk and surface origins for waveguiding losses are discussed based on the film structure.
- Jpn J Appl Phys
Jpn J Appl Phys 46(4A), 1543-1548, 2007-04-15
INSTITUTE OF PURE AND APPLIED PHYSICS