Multifunction integrated optical circuit with a high polarization extinction ratio on TFLN for a 1310  nm interferometric fiber optic gyroscope

For an interferometric fiber optic gyroscope (IFOG), the polarization extinction ratio (PER) is a pivotal parameter influencing angular velocity measurement accuracy. In this paper, we propose and demonstrate a multifunction integrated optical circuit (MIOC) with high PER and high modulation efficiency on a thin-film lithium niobate platform for IFOG at the 1310 nm band. This MIOC monolithically integrates two optical power splitters, two phase modulators, and a composite polarizer constructed with a tapered waveguide, two semicircular bent waveguides, and a multimode interference coupler. Additionally, a metal absorption layer is introduced to prevent the leaked light from coupling into the waveguide or the subsequent optical fiber again. Leveraging this configuration, a maximum PER of 45 dB is demonstrated experimentally. Meanwhile, a high modulation efficiency of <i>V</i>_π⋅<i>L</i>=1.34<i>V</i>⋅<i>c</i><i>m</i> is also achieved.