Thermal characterization of electrical tracing-assisted dual-microring optical sensors

In this paper, we study the temperature sensitivity of an electrical tracing-assisted dual-microring optical sensor, which consists of a sensing ring to detect the refractive index change on its surface and a tracing ring to trace the resonance wavelength shift of the sensing ring by the thermo-optic effect with a heating electrode on it. The wavelength shift measurement is therefore changed to electrical power variation measurement. Thanks to the real-time compensation effect of the tracing ring, the temperature dependence of the sensor is found to be intrinsically low. The resonance wavelength temperature sensitivity difference between the two rings is measured to be as low as 10.1 pm/°C, showing that the temperature dependence of the sensor in terms of wavelength per degree is reduced by ~6 times compared to that of a single ring sensor. The temperature sensitivity of the sensor in terms of electrical power per degree is measured to be -0.077 mW/°C. By using tracing ring with enhanced tuning efficiency, this value can be further decreased to -0.0057 W/°C. The experimental results agree well with the expectation. This type of sensors with low temperature dependence has great potential to be deployed in various practical point-of-care diagnostic applications.