600-Hz linewidth short-linear-cavity fiber laser

Area of Science:

• Optics and Photonics
• Laser Physics

Background:

• Spatial hole burning (SHB) is a detrimental effect in fiber lasers that can degrade performance.
• Traditional fiber laser designs often struggle to mitigate SHB effectively.
• Improving resonator design is crucial for enhancing laser stability and spectral purity.

Purpose of the Study:

• To propose and demonstrate a novel short-linear-cavity (SLC) fiber laser design.
• To reduce the spatial hole burning (SHB) effect in fiber lasers.
• To achieve a narrow laser linewidth and investigate the impact of resonator design on laser dynamics.

Main Methods:

• Utilized a virtual-folded-ring (VFR) resonator to control polarization states of counter-propagating waves, mitigating SHB.
• Incorporated a fiber Bragg grating Fabry-Perot (FBG FP) filter to extend photon lifetime via multi-reflection.
• Analyzed laser dynamics, including relaxation oscillation frequency and linewidth, under the influence of slow light effects.

Main Results:

• Successfully reduced the spatial hole burning (SHB) effect by employing the VFR structure.
• Extended the photon lifetime within the resonator due to multi-reflection in the FBG FP.
• Achieved a narrow laser linewidth of less than 600 Hz.
• Observed a relaxation oscillation frequency of approximately 160 kHz, attributed to slow light.

Conclusions:

• The proposed SLC fiber laser design effectively suppresses SHB and enhances intra-cavity power.
• The VFR resonator and FBG FP filter combination leads to improved laser performance, including a narrow linewidth.
• The slow light effect plays a significant role in the observed relaxation oscillation frequency.