Ultrahigh-quality-factor silicon-on-insulator microring resonator

Area of Science:

• Photonics
• Materials Science
• Optical Engineering

Background:

• Silicon-on-insulator (SOI) microring resonators are crucial optical components.
• Achieving ultrahigh quality factors (Q) is essential for advanced photonic integrated circuits.
• Directly structured semiconductor microrings often face limitations in Q factor due to surface roughness.

Purpose of the Study:

• To develop ultrahigh-Q SOI microring resonators utilizing silicon wire waveguides.
• To analytically investigate the critical coupling condition for optimizing device performance.
• To demonstrate record-breaking Q factors and low propagation losses in curved SOI waveguides.

Main Methods:

• Fabrication of silicon microring resonators on SOI substrates.
• Utilizing silicon wire waveguides with small bending radii.
• Derivation of an analytical model to describe device characteristics.
• Experimental measurement of propagation loss and Q factor.

Main Results:

• Demonstrated propagation losses as low as 1.9 ± 0.1 dB/cm in a 20 µm bending radius curved waveguide.
• Achieved an ultrahigh Q factor of 139,000 ± 6,000.
• These results represent the highest reported values for curved SOI waveguide devices and directly structured semiconductor microrings without post-fabrication smoothing.

Conclusions:

• Ultrahigh-Q SOI microring resonators can be achieved through careful design and fabrication.
• Low propagation loss and critical coupling are vital for optimizing microring resonator performance.
• The demonstrated device performance sets a new benchmark for directly structured semiconductor microring resonators.