Ultra-sensitive silicon temperature sensor based on cascaded Mach–Zehnder interferometers

An ultra-sensitive temperature sensor without sacrificing detection range is demonstrated on the silicon-on-insulator (SOI) platform using cascaded Mach–Zehnder interferometers (MZIs). The sensitivity enhancement is achieved by tailoring the geometric parameters of the two MZIs to have similar free spectral ranges (FSRs) but quite different sensitivities. The proposed sensor only needs single lithography for the sensing unit, without introducing negative thermo-optic coefficient (TOC) materials. The measured sensitivity is 1753.7 pm/°C from 27°C to 67°C, which is higher than any reported results on a silicon platform and about 21.9 times larger than conventional all-silicon temperature sensors.