Post-fabrication resonance trimming of Si<sub>3</sub>N<sub>4</sub> photonic circuits via localized thermal annealing of a sputter-deposited SiO<sub>2</sub> cladding
Yanran Xie, Henry C. Frankis, Jonathan D. B. Bradley, Andrew P. Knights
Abstract
We report a resonance trimming technique, applicable to waveguides employing an SiO 2 cladding. The SiO 2 is deposited by a room temperature sputtering process. Resonance shifts of micro-ring resonators of 4.4 nm were achieved with furnace annealing, whereas a resonance shift of 1.4 nm was achieved using integrated micro-heaters. For our device layout, with 30 μ m ring separation, the thermal cross-talk is negligible, and isolated trimming of each micro-ring is achieved. Three, single-channel ring filters on the same substrate were aligned to the same wavelength within a 20 pm precision. The stability of trimmed micro-rings was assessed following extended storage in atmospheric ambient. For a ring shifted by 4.4 nm using furnace annealing, relaxation of 540 pm is observed, while for a ring shifted by 1.4 nm using integrated heaters, the relaxation is 270 pm.