Dual-laser self-injection locking to an integrated microresonator.

Area of Science:

• Photonics and Optical Engineering
• Laser Physics and Technology
• Microresonator Devices

Background:

• Diode laser self-injection locking (SIL) is crucial for narrowing laser linewidth and suppressing high-frequency noise.
• Existing SIL techniques have been limited to single lasers, hindering advancements in multi-frequency laser applications.
• High-demand applications in telecommunications, quantum technologies, and microwave photonics require multi-frequency, narrow-linewidth laser sources.

Purpose of the Study:

• To experimentally demonstrate dual-laser SIL using two multifrequency laser diodes and an integrated silicon nitride microresonator.
• To investigate the nonlinear interactions between two lasers locked to different modes of the microresonator.
• To explore the potential for simultaneous frequency and phase stabilization and coherent addition of dual-laser outputs.

Main Methods:

• Experimental implementation of dual-laser self-injection locking to different whispering gallery modes of a silicon nitride microresonator.
• Observation and analysis of spectral collapse, linewidth narrowing, and high-frequency noise suppression for both lasers.
• Theoretical modeling of dual-SIL and investigation of inter-laser nonlinear effects within the microresonator.

Main Results:

• Successful demonstration of dual-laser SIL, achieving simultaneous spectrum collapse, linewidth narrowing, and noise suppression for both diodes.
• Observation of strong nonlinear interactions between the two laser fields due to the shared microresonator.
• Demonstration that locking both lasers to the same microresonator mode results in simultaneous frequency and phase stabilization and coherent output addition.

Conclusions:

• Dual-laser SIL to microresonators is a viable method for generating high-quality, multi-frequency laser sources.
• The demonstrated technique offers a pathway to advanced photonic systems requiring stable, coherent, and narrow-linewidth multi-laser outputs.
• This work lays the foundation for novel applications in telecommunications, quantum information processing, and microwave photonics.