Narrow Linewidth Half-Open-Cavity Random Laser Assisted by a Three-Grating Ring Resonator for Strain Detection

Area of Science:

• Photonics and Optical Engineering
• Fiber Optic Sensing
• Laser Physics

Background:

• Fiber lasers are crucial for sensing applications.
• Achieving narrow linewidth and high stability in fiber lasers remains a challenge.
• Existing methods often struggle with resolution in dynamic strain measurement.

Purpose of the Study:

• To propose and experimentally investigate a stabilized narrow-linewidth random fiber laser for enhanced strain detection.
• To leverage a three-grating ring (TGR) resonator and half-open-cavity structure for improved laser performance.
• To achieve high resolution in dynamic strain measurements using a novel fiber laser design.

Main Methods:

• Development of a three-grating ring (TGR) resonator incorporating a double-cavity fiber Bragg grating Fabry-Perot (FBG-FP) interferometer.
• Implementation of a half-open-cavity structure to enhance optical gain from erbium-doped fiber.
• Experimental characterization of laser linewidth, frequency noise, and dynamic strain resolution.

Main Results:

• A stable ultra-narrow linewidth of approximately 205 Hz was achieved.
• Frequency noise was significantly reduced to about 2 Hz/√Hz.
• A high dynamic strain measuring resolution of 35 femto-strain (fε)/√Hz was demonstrated.

Conclusions:

• The proposed TGR resonator with a half-open-cavity structure effectively stabilizes narrow-linewidth random fiber laser output.
• The design enhances photon lifetime and narrows linewidth by utilizing double optical gain.
• The system offers a promising solution for high-resolution dynamic strain sensing applications.