Self-injection locked sub-hertz Brillouin laser enabled by a Möbius-type ring resonator

Area of Science:

• Photonics and Laser Technology
• Optical Engineering
• Materials Science

Background:

• Stimulated Brillouin scattering (SBS) is vital for narrow-linewidth lasers, enhancing coherence and reducing phase noise.
• Conventional Brillouin lasers necessitate complex optical frequency stabilization, increasing cost and setup complexity.
• Self-injection locking offers a simplified and cost-effective alternative for laser stabilization.

Purpose of the Study:

• To demonstrate a simplified self-injection locking technique for narrow-linewidth laser generation.
• To introduce a novel Möbius-type ring resonator for enhanced laser performance.
• To achieve cost-effective production of narrow-linewidth lasers.

Main Methods:

• Fabrication of a Möbius-type ring resonator using polarization-maintaining fiber with a 90° splice and a single coupler.
• Utilizing the unique cavity design where pump light circulates twice, separating modes for self-injection locking and stable laser output.
• Applying the self-injection locking technique to a 1310 nm distributed feedback (DFB) laser.

Main Results:

• Successful implementation of self-injection locking using a single coupler.
• Narrowing the Lorentzian linewidth of the 1310 nm DFB laser to 8.00 (±2.02) Hz.
• Achieving a linewidth of 890 (±350) mHz for the generated Brillouin laser.

Conclusions:

• The Möbius-type ring resonator enables effective self-injection locking with a simplified, single-coupler setup.
• This method significantly reduces linewidth, offering a highly cost-effective approach to narrow-linewidth laser generation.
• The demonstrated technique presents a promising solution for applications requiring high-coherence, low-phase-noise lasers.