Refractive Index Changes in Mach-Zehnder Waveguide Interferometers for Biological Applications

This work presents the simulation and fabrication of different Mach-Zehnder waveguide interferometers (MZWIs) on fused silica substrates manufactured through femtosecond direct laser writing (FDLW). Rotated interferometers were created such that one of the arms is written near the interaction surface, where the sensing region has a length of 1, 3 or 6 mm. The results show that by varying the sensing region dimensions, we can control the device's sensitivity. The interferometer was designed in an unbalanced configuration, with the shorter arm containing this sensing region and the longer arm allowing us to generate a geometric path difference of approximately 33 µm. This facilitates the generation of an interference pattern over a wavelength scanning range from 1470 to 1560 nm.