Rebeka Leon

Major: Engineering

Mentors: Amalu Shimamura, Galan Moody

Characterization of Silicon Nitride Unbalanced Mach-Zehnder Interferometers

Silicon nitride (SiN) waveguides are widely used for their low optical loss and high refractive index contrast. One potential application is a SiN magnetometer designed to measure small magnetic field fluctuations for geo-positioning, navigation, and sensing. The characterization of photonic devices is important for evaluating their performance before their use in quantum photonics applications. Our research involves the characterization of SiN unbalanced Mach-Zehnder interferometers (UMZIs) which contain directional couplers designed to split optical power with a 50:50 ratio. Fabrication variations can cause the actual power coupling coefficients to differ from the intended designs, making characterization necessary to ensure that the device performs as designed. We measured the optical transmission measurements from all different input and output port combinations and analyzed the data to determine the extinction ratios. These measurements were then used to extract the power coupling coefficients and waveguide propagation loss. Our results show that across different free spectral ranges (FSRs), the power coupling coefficients were close to the simulated value of 50%, indicating minimal fabrication variation. These findings demonstrate that the directional couplers perform as designed and support their use for quantum photonics applications such as magneto-optic Mach-Zehnder interferometer sensors.