Millihertz-linewidth self-injection-locked semiconductor laser based on a hollow FP cavity

Area of Science:

• Optics and Photonics
• Quantum Technologies
• Laser Physics

Background:

• Ultra-narrow-linewidth lasers are essential for high-precision applications like optical atomic clocks and quantum communications.
• Semiconductor lasers offer a compact and cost-effective platform, but achieving ultra-narrow linewidths has been challenging.

Purpose of the Study:

• To report an ultra-narrow-linewidth self-injection locked semiconductor laser.
• To demonstrate a record intrinsic linewidth for self-injection locked lasers.
• To validate the laser's performance for advanced coherent optical systems.

Main Methods:

• Optical feedback from a high-Q (258 million) three-mirror Fabry-Perot (FP) cavity was used for self-injection locking.
• A delay self-heterodyne method with a signal source analyzer was employed to measure phase noise and linewidth.
• Output power was measured at 12 mW.

Main Results:

• An ultra-narrow-linewidth semiconductor laser with an intrinsic linewidth of 3 mHz was achieved.
• The laser exhibited a phase noise of -129 dBc/Hz at 100 kHz offset frequency.
• An estimated integral linewidth of 11.8 Hz was recorded, confirming extremely low noise.

Conclusions:

• The developed self-injection locked semiconductor laser demonstrates a record intrinsic linewidth.
• The laser's performance offers significant potential for extra-laboratory applications in coherent optical systems.
• This work advances the development of narrow-linewidth lasers for quantum technologies and precision measurement.