On-chip simultaneous sensing of humidity and temperature with a dual-polarization silicon microring resonator

It is still challenging to realize an on-chip optical sensor that can detect humidity and temperature at the same time. In this paper, we demonstrate a silicon-based dual-polarization micro-ring resonator (MRR) with a polyvinyl-alcohol (PVA) upper-cladding, which enables the simultaneous measurement of humidity and temperature. Due to the significant polarization-dependence of the silicon-on-insulator (SOI) nanophotonic waveguide, the transverse electric (TE) and transverse magnetic (TM) polarization modes have quite different sensitivities towards the changes of ambient relative humidity (RH) and temperature. Sensitivity, resolution, stability and cross-sensitivity are analyzed for the present dual-parameter sensor. The RH and temperature response sensitivity are measured to be 97.9 pm/%RH, 325.1 pm/%RH, 69.0 pm/°C and 30.6 pm/°C for TE and TM polarizations, respectively. To the best of our knowledge, it is the first on-chip optical sensor enabling the simultaneous measurement of RH and temperature.