Microfiber knot resonator with 10⁷ Q-factor record.

Area of Science:

• Photonics
• Materials Science
• Optical Engineering

Background:

• Ultra-high-quality-factor (UHQ) resonators are crucial for advanced photonic applications.
• Existing UHQ resonators are not compatible with all-fiber systems.
• Microfiber resonators face challenges in achieving UHQ due to mechanical properties and coupling issues.

Purpose of the Study:

• To fabricate an UHQ microfiber knot resonator (MKR) compatible with all-fiber frameworks.
• To overcome the Q-factor limitations in microfiber resonators.
• To demonstrate the application of UHQ-MKR in all-fiber lasers.

Main Methods:

• Developed a fabrication model for UHQ microfiber knot resonators (MKRs).
• Controlled environmental parameters to produce high-quality microfibers with uniform stress and low loss.
• Investigated coupling mechanisms experimentally and theoretically.

Main Results:

• Achieved a record Q-factor of 3.9 × 10⁷, an improvement of three orders of magnitude.
• Demonstrated stable and reproducible fabrication of UHQ-MKRs.
• Successfully applied the UHQ-MKR in an all-fiber laser to achieve narrow-linewidth single-frequency operation.

Conclusions:

• The developed UHQ-MKR fabrication model addresses the Q-factor bottleneck in microfiber resonators.
• This research opens a new era for UHQ microfiber resonators exceeding the 10⁷ level.
• The UHQ-MKR shows significant potential for precision and efficiency in microfiber guiding-wave photonics.