Microring-resonator-based add-drop filters in SiN: fabrication and analysis

Area of Science:

• Photonics and Optical Engineering
• Materials Science

Background:

• Microring resonators are crucial components in optical filtering.
• High-order filters typically require complex designs like the Vernier effect to achieve desired performance.

Purpose of the Study:

• To fabricate and characterize third-order add-drop filters using series-coupled microring resonators.
• To demonstrate low insertion loss and wide free spectral range in a high-order filter without the Vernier effect.

Main Methods:

• Fabrication of silicon-rich silicon nitride microring resonators with precise dimensional control and minimal sidewall roughness.
• Design and simulation of third-order add-drop filter configurations.
• Experimental characterization of filter performance, including drop loss and free spectral range.

Main Results:

• Achieved a low 3 dB drop loss, a first for high-order microring filters without the Vernier effect.
• Demonstrated a wide 24 nm free spectral range.
• Numerical simulations accurately matched experimental spectral responses, identifying design-related non-idealities.

Conclusions:

• The developed silicon nitride microring resonator filters offer a promising solution for efficient optical add-drop multiplexing.
• Design-based corrections can address non-ideal port responses, enhancing filter performance.
• This work advances the capabilities of integrated photonic filters.