Tantalum pentoxide (Ta2O5) based athermal micro-ring resonator

By analyzing the temperature-dependent transmission spectrum of a Ta2O5 micro-ring resonator, the thermal-optical coefficient at the optical communication wavelength regime has been determined. The temperature-dependent resonance wavelength shift of the resonator with radius 50 µm was measured as 7.8 pm/K, and the thermal-optical coefficient at ∼1543 nm was estimated to be 6×10−6 /K. Furthermore, a power-dependent transmission of the micro-ring resonator was performed to characterize the effects of local heating and nonlinear absorption. No significant power-dependent wavelength shift and asymmetric response were observed in the optical wavelength up to 125 mW. This suggests the absence of nonlinear absorption and thermal expansion effects in the Ta2O5 ring resonator. The Ta2O5 waveguide is potentially a superior candidate for applications in optical communication systems or high-power nonlinear waveguides due to its thermal stability, thermal insensitivity, and absence of nonlinear absorption.