Self Q-switched single-frequency all-fiber laser.

Area of Science:

• Fiber laser technology
• Nonlinear optics
• Quantum electronics

Background:

• Development of stable, narrow-linewidth pulsed fiber lasers is crucial for various applications.
• Traditional methods for achieving single-frequency (SF) operation often involve complex setups.
• Integrating saturable absorbers (SAs) within the laser cavity can enable self-Q-switching for pulsed operation.

Purpose of the Study:

• To propose and demonstrate a self Q-switched single-frequency (SF) all-fiber laser.
• To utilize the co-doped Er:Yb fiber as both the gain medium and a fiber-type saturable absorber (SA).
• To achieve stable SF operation using a cascade sub-cavity design.

Main Methods:

• Employing an intra-cavity Er:Yb co-doped fiber for lasing and self-Q-switching via ground-state reabsorption.
• Constructing a cascade sub-cavity using two 3 dB optical couplers (OCs) for narrow-bandwidth mode selection.
• Utilizing a fiber-type SA with a high damage threshold to achieve microjoule pulse energy.

Main Results:

• Obtained microjoule-level self-Q-switched SF pulses with a narrow linewidth of ~252 kHz.
• Measured pulse width of ~1.766 µs, resulting in a time-bandwidth product close to the Gaussian transform limit (~0.445).
• Achieved a maximum output power of ~100 mW for the pulsed SF laser, with tunable wavelength via fiber Bragg grating (FBG) stretching.

Conclusions:

• The proposed self Q-switched SF all-fiber laser offers a compact and efficient solution for generating high-quality pulses.
• The integrated fiber-type SA and cascade sub-cavity design effectively achieve stable SF pulsed operation.
• The demonstrated tunability and performance characteristics make this laser suitable for diverse photonic applications.