Design and fabrication of Mach-Zehnder interferometers in soda-lime glass for temperature sensing applications

High sensitivity represents one of the main goals that sensing devices need to satisfy for their applications. This work presents to the best of our knowledge the first integrated Mach-Zehnder interferometer (MZI) embedded in soda-lime glass with comparable sensitivity to silicon-on-insulator (SOI) devices. We manufactured the MZIs by the femtosecond direct laser writing (FDLW) technique and characterized them with temperature. Four buried MZIs were manufactured by slightly increasing the optical path due to separation between the arms of the interferometer ( ). We achieved a fringe shift of ∼8 for an increase of 0.18 µm. We have characterized one of these devices with temperature from 30°C to 70°C obtaining a sensitivity of ∼28 / . We improved the sensitivity of the device to ∼54 / due to the advantage of the unique three-dimensional (3D) capabilities that FDLW provides, overcoming the characteristically low thermo-optic coefficient of soda-lime glass just by rotating the MZI structure 11°.