Demonstration of Ultra-High-Q Silicon Microring Resonators for Nonlinear Integrated Photonics

Area of Science:

• Photonics
• Materials Science
• Optical Engineering

Background:

• Silicon microring resonators are key components in integrated photonics.
• Achieving ultra-high quality factors (Q-factors) is essential for enhancing nonlinear optical processes.
• Minimizing waveguide loss is critical for device performance.

Purpose of the Study:

• To fabricate ultra-high-Q silicon microring resonators using a novel fabrication process.
• To investigate the impact of waveguide width on resonator performance and loss.
• To demonstrate the improvement in four-wave mixing (FWM) conversion efficiency due to reduced waveguide loss.

Main Methods:

• Fabrication of silicon microring resonators utilizing a reflowing photoresist and oxidation smoothing process.
• Characterization of resonator Q-factors and waveguide losses across a range of wavelengths near 1550 nm.
• Theoretical and experimental analysis of four-wave mixing conversion efficiency in relation to waveguide loss.

Main Results:

• Achieved ultra-high average Q-factors of up to 1.20 × 10⁶ for microring resonators.
• Demonstrated low waveguide losses of approximately 0.27-0.28 dB/cm.
• Observed a significant improvement in four-wave mixing conversion efficiency, reaching -17.0 dB at 6.50 dBm pump power, attributed to reduced waveguide loss.

Conclusions:

• The reflowing photoresist and oxidation smoothing process enables the fabrication of ultra-high-Q silicon microring resonators.
• Reduced waveguide loss directly enhances the conversion efficiency of four-wave mixing.
• These findings pave the way for more efficient nonlinear photonic devices.