Ultracompact high-Q whispering gallery mode microresonator in a non-closed waveguide path

Area of Science:

• Photonics and Optical Engineering
• Integrated Photonics
• Microresonator Technology

Background:

• High-performance traveling-wave optical resonators are essential for integrated photonic circuits.
• Conventional whispering-gallery mode microresonators (WGMRs) have large footprints due to their closed-loop waveguide paths.

Purpose of the Study:

• To report an ultracompact, high-loaded Q silicon photonic WGMR utilizing an open curved path.
• To demonstrate a novel approach for achieving high Q-factors in a minimized device size.

Main Methods:

• Leveraging spatial mode multiplexing and low-loss mode converter-based photonic routers.
• Implementing reentrant photon recycling within a single non-closed waveguide.
• Fabricating a silicon photonic device with an open-path design.

Main Results:

• Achieved a measured loaded Q-factor of 1.78 × 10^5 at 1554.3 nm.
• Device footprint is 0.00137 mm², significantly smaller than standard WGMRs.
• Demonstrated a 100× higher Q-factor compared to photonic crystal counterparts.

Conclusions:

• Pioneered dense integration of high-performance WGMR arrays through open-path mode recirculation.
• The ultracompact WGMR offers a pathway to miniaturized and high-performance photonic integrated circuits.
• This open-path approach overcomes the size limitations of conventional WGMRs.