Waveguide Mach-Zehnder Interferometer for Temperature and Concentration Sensing

Mach-Zehnder interferometer (MZI) based on optical waveguide is proposed and demonstrated, in which a waveguide core with a core expander and a collector is inscribed in a photoresist SU-8 film by ultrafast laser-induced two-photon polymerization (TPP) technique, whereas the cladding of the waveguide is fabricated by the standard photolithographic technique. Interference occurs in this MZI when the light is scattered into the cladding by the core expander and then collected by the core collector, in which the roles of the core expander and the collector are investigated in details. By integrating with a microchannel, a waveguide-based optofluidic MZI sensor is realized, which exhibits a redshift at a sensitivity of 0.618 nm/°C with the increase of temperature, and blueshifts at sensitivities of -0.102 nm/wt% and -0.092 nm/°Bx for concentration measurement of sodium chloride and sucrose solutions, respectively. Experimental results demonstrate the effectiveness of this sensor for temperature and concentration measurement, manifesting its promising potential for biomedical, chemical, and environmental applications.