High-order microring resonators with bent couplers for a box-like filter response

Area of Science:

• Photonics and Optical Engineering
• Integrated Optics
• Microwave Engineering

Background:

• Microring resonator (MRR) filters are crucial components in optical communication systems.
• Achieving a precise, box-like filter response with sharp edges and high extinction ratios is a significant challenge in filter design.

Purpose of the Study:

• To propose and demonstrate high-order microring resonator filters with bent directional couplers.
• To achieve a box-like filter response with improved performance metrics.
• To investigate the thermal tunability of the proposed filter design.

Main Methods:

• Design and fabrication of five-microring filters incorporating bent directional couplers.
• Characterization of filter response, including excess loss, out-of-band extinction ratio, and edge steepness.
• Demonstration of thermal tunability using a Titanium (Ti) microheater.

Main Results:

• The fabricated filters exhibit a box-like response with sharp rising and falling edges (48 dB/nm).
• Achieved an out-of-band extinction ratio of approximately 36 dB.
• Demonstrated low excess loss (<1.0 dB) and a thermal tuning efficiency of ~0.10 nm/mW.

Conclusions:

• Bent directional couplers enable easy adjustment of the coupling ratio without altering the microring perimeter.
• The proposed high-order MRR filters with bent couplers offer superior performance for optical filtering applications.
• The demonstrated thermal tunability provides a pathway for active control and wavelength tuning of these filters.