Integrated chip-scale Si_3N_4 wavemeter with narrow free spectral range and high stability

We designed, fabricated, and characterized an integrated chip-scale wavemeter based on an unbalanced Mach–Zehnder interferometer with 300 MHz free spectral range. The wavemeter is realized in the ${\mathrm{Si}}_3{\mathrm{N}}_4$ platform, allowing for low loss with $\sim 62\mathrm{cm}$ of on-chip delay. We also integrated an optical hybrid to provide phase information. The main benefit of a fully integrated wavemeter, beside its small dimensions, is increased robustness to vibrations and temperature variations and much improved stability over fiber-based solutions.