Ultra-high quality factor planar Si3N4 ring resonators on Si substrates

Area of Science:

• Photonics and Optical Engineering
• Materials Science
• Microwave Photonics

Background:

• High-quality factor (Q) optical resonators are crucial for various photonic devices.
• Silicon nitride (Si3N4) offers excellent optical transparency and low propagation loss.
• Achieving ultra-high Q factors in planar Si3N4 ring resonators is a key challenge.

Purpose of the Study:

• To demonstrate ultra-high Q factor planar Si3N4 ring resonators.
• To integrate these resonators with directional couplers for optical filter applications.
• To achieve ultra-narrow bandwidths in optical add-drop and notch filters.

Main Methods:

• Fabrication of planar Si3N4 ring resonators.
• Integration with laterally offset planar waveguide directional couplers.
• Characterization of resonator Q factors and filter bandwidths at 1060 nm, 1310 nm, and 1550 nm.

Main Results:

• Demonstrated ultra-high Q factors of 19 million, 28 million, and 7 million at 1060 nm, 1310 nm, and 1550 nm.
• Achieved ultra-narrow bandwidths of 16 MHz, 38 MHz, and 300 MHz for optical add-drop and notch filters.
• Reported the highest Q factors for ring resonators with planar directional couplers to date.

Conclusions:

• The demonstrated Si3N4 ring resonators offer unprecedented Q factors.
• These high-Q resonators are suitable for realizing ultra-narrowband optical filters.
• The technology paves the way for ultra-narrowband microwave photonic filters.