|
The field of integrated photonics has expanded since the last century due to the need for even smaller devices, finding numerous applications in areas such as sensing, communications, and information technology. Particularly, the use of optical sensors has increased in recent years due to advantages over classical sensors, including versatility, minimal sample quantities, and label-free quantitative detection of chemical and biological samples. One technique employed for creating integrated photonic structures is ultrashort laser inscription, enabling the fabrication of optical waveguides in transparent materials without the need for masks or chemical processes. This work presents significant advancements in the design, fabrication, and characterization of Mach-Zehnder interferometers (MZIs) based on optical waveguides, utilizing the femtosecond direct laser writing (FDLW) technique. These interferometers have enabled the creation of integrated systems and their application in detecting physical variables such as temperature changes and variations in the refractive index of solutions with varying concentrations, including urea. We manufactured an embedded Mach-Zehnder interferometer in soda-lime glass, exhibiting sensitivity comparable to Silicon-on-Insulator (SOI) devices. A substantial enhancement in sensitivity (~54 pm/°C) was achieved, thanks to the unique three-dimensional (3D) capabilities provided by FDLW, surpassing the typically low thermo-optic coefficient of soda-lime glass. As a proof of concept, we also applied the first FDLW-fabricated MZI for concentration changes detection through evanescent field interaction in fused silica, demonstrating a sensitivity of ~1.22 nm/mM. Such miniaturized structures will significantly impact the development of compact and highly sensitive integrated photonic devices.
|
