Abstract

Tantalum pentoxide (Ta₂O₅) of a large bandgap material has recently utilized to demonstrate nonlinear optical waveguide applications due to its superior linear and nonlinear optical properties [1][2], including low absorption loss coefficient in visible to infrared regions, high Kerr coefficients, and free of nonlinear absorption. In this work, the thermal-optical coefficient of tantalum pentoxide has been investigated experimentally by using a micro-ring resonator structure. Taking the advantage of index-sensitively property of ring resonator, the material with ultralow thermal-optical coefficient is easily to be measured and analyzed by using a ring waveguide structure. The cross-section of Ta₂O₅ based micro-ring resonator is set as 1.5μm*0.7μm, and the diameter of ring resonator is set as 100μm. By increasing the substrate temperature of micro-ring resonator, the variation of resonant wavelength of micro-ring resonator is recorded accordingly. The central wavelength of micro-ring resonator is red-shifted from 1543.430 nm to 1543.586 nm when the substrate temperature increases from 20 to 40°C. By considering the thermal-optical and thermal expansion effect of micro-ring resonator, the thermal-optical coefficient of Ta₂O₅ is estimated to be 6.8×10⁻⁶ / K at ~1550 nm. The thermal-optical coefficient of Ta₂O₅ is ten times of magnitude less than those of conventional III–V semiconductors, indicating that Ta₂O₅ supports the development of thermal-insensitive devices, such as sub-multiplexer and filter element.

© 2017 Japan Society of Applied Physics, Optical Society of America