Temperature dependence of refractive index of Ta2O5 dielectric films

The temperature dependence of refractive index of tantalum pentoxide (Ta2O5) dielectric films was investigated experimentally. The films were formed by a magnetron radio frequency sputtering technique on the Si substrates. After deposition, the film was fabricated into an antiresonant reflecting optical waveguide using a novel wet etching technique. The thermal variation of refractive index of Ta2O5 was characterized by measuring the index-vs-temperature coefficient of the antiresonant reflecting optical waveguide with a Mach-Zehnder interferometry system. The measured result was 2.3 x 10(-6) 1/K at 632.8 nm from 298 to 328K. This result indicates that index-vs-temperature coefficient of the Ta2O5 dielectric films is about ten times less than those of conventional III-V semiconductors.