High quality factor subwavelength grating waveguide micro-ring resonator based on trapezoidal silicon pillars.

Area of Science:

• Photonics and Optical Engineering
• Materials Science

Background:

• Subwavelength grating waveguide-based micro-ring resonators (SWGMRs) are crucial for light-matter interaction research.
• Achieving high quality factors in small-radius (5 μm) SWGMRs is challenging due to significant bend loss.

Purpose of the Study:

• To investigate the use of trapezoidal silicon pillars to reduce bend loss in SWGMRs.
• To enhance the quality factor of small-radius SWGMRs through optimized pillar geometry.

Main Methods:

• Fabrication of SWGMRs using trapezoidal silicon pillars instead of conventional rectangular ones.
• Experimental characterization of the quality factor and propagation loss of the fabricated resonators.

Main Results:

• Demonstrated a 5 μm radius trapezoidal SWGMR (T-SWGMR) with a quality factor of 11,500, a 4.6x improvement over conventional designs.
• Achieved an 81.4% reduction in propagation loss compared to rectangular pillar SWGMRs.
• A 10 μm radius T-SWGMR exhibited a quality factor of 45,000, indicating a low propagation loss of 6.07 dB/cm.

Conclusions:

• Trapezoidal silicon pillars effectively reduce bend loss in SWGMRs by creating an asymmetric effective refractive index profile.
• This approach significantly enhances the quality factor of small-radius SWGMRs, making them more practical for applications.
• The method is scalable and applicable to larger radius SWGMRs, broadening its utility in photonic devices.