Photonic thermometer with a sub-millikelvin resolution and broad temperature range by waveguide-microring Fano resonance.

Fano resonance theoretically is an effective approach for sensitivity enhancement in photonic sensing applications, but the reported methods suffer from complicated structure and fabrication, narrow dynamic range, etc. In this article, we propose a photonic thermometer with sub-millikelvin resolution and broad temperature measurement range implemented by a simple waveguide-microring Fano structure. An air hole is introduced at the center of the coupling region of the waveguide of an all-pass microring resonator.