Multilayer dielectric materials of SiO X/Ta 2O 5/SiO 2 for temperature-stable diode lasers

Abstract

A novel athermal waveguide for temperature-stable diode lasers was investigated. The waveguide consisted of SiO X , Ta 2O 5 and SiO 2 dielectric layers deposited on a Si substrate. A theoretical calculation shows that the optical path (defined by the product of the effective index of the waveguide and the waveguide length) of the waveguide can be independent of temperature if the thicknesses of Ta 2O 5 and SiO X layers are properly chosen. The Ta 2O 5 and SiO X layers were deposited using the magnetron sputtering technique. The indices of SiO x and Ta 2O 5 films are 1.5 and 2.12, respectively. The SiO 2 layer was fabricated by flame hydrolysis deposition with a thickness of 4 μm. Good surface morphology and thickness uniformity of the SiO 2 layer were obtained. The index-temperature drift of SiO 2 was measured to be 3 × 10 −5/ °C which is about 10 times less than that of a III–V semiconductor. A comparison of the temperature dependence of the SiO X /Ta 2O 5/SiO 2 waveguide and Ta 2O 5/TiO 2/SiO 2 waveguide is also presented.