Laser diode self-injection locking to an integrated high-Q Fabry-Perot microresonator

Area of Science:

• Photonics and Optical Engineering
• Materials Science

Background:

• Self-injection locking (SIL) is key for compact, narrow-linewidth lasers.
• Microresonators offer high quality factors and large mode volumes, reducing noise.
• Thermorefractive noise (TRN) is a fundamental limitation in lasers.

Purpose of the Study:

• To extend self-injection locking (SIL) to chip-integrated Fabry-Perot (FP) microresonators.
• To develop a theoretical model and experimentally validate SIL with FP microresonators.
• To achieve a fundamental thermorefractive-noise-limited laser on a chip.

Main Methods:

• Fabrication of silicon nitride FP microresonators with photonic crystal reflectors using ultraviolet lithography.
• Implementation of evanescent side-coupling for precise tuning of the SIL feedback mechanism.
• Development of a theoretical model to describe the SIL phenomenon in FP microresonators.

Main Results:

• Experimental demonstration of self-injection locking (SIL) to chip-integrated FP microresonators.
• Achieved a laser performance limited by fundamental thermorefractive noise (TRN).
• Excellent agreement between the theoretical model and experimental results.

Conclusions:

• Self-injection locking (SIL) is successfully extended to chip-integrated Fabry-Perot (FP) microresonators.
• The developed technique enables compact, low-noise laser systems with TRN-limited performance.
• Results are highly relevant for advancing chip-scale laser technology.