Highly efficient, depressed-cladding thulium-doped fiber laser at 1762 nm

Area of Science:

• Fiber laser technology
• Optoelectronics
• Laser physics

Background:

• Continuous-wave (CW) fiber lasers operating in the 1.7-μm range are crucial for various applications.
• Mitigating long-wavelength amplified spontaneous emission (ASE) is a key challenge in achieving high-power 1.7-μm fiber lasers.
• Thulium-doped fibers (TDFs) are commonly used gain media for this wavelength range.

Purpose of the Study:

• To demonstrate a multi-watt-level, continuous-wave (CW) all-fiber laser operating at 1.76-μm.
• To investigate the use of in-house-drawn depressed-cladding Tm-doped fiber (dc-TDF) as an active medium to suppress amplified spontaneous emission (ASE).
• To achieve high output power and efficiency using resonant pumping.

Main Methods:

• Utilized a linear cavity configuration for the all-fiber laser.
• Employed an in-house-drawn depressed-cladding Tm-doped fiber (dc-TDF) as the active gain medium.
• Implemented resonant pumping at 1.56-μm to excite the thulium ions.

Main Results:

• Achieved a continuous-wave (CW) output power of 2.47 W in a linear cavity configuration.
• Demonstrated a high slope efficiency of 75.8% relative to launched power.
• Attained over 4 W output power with bidirectional pumping and a slope efficiency of 66%.
• Maintained an optical signal-to-noise ratio (SNR) exceeding 65 dB.

Conclusions:

• Successfully demonstrated the first 1.7-μm laser operation utilizing depressed-cladding Tm-doped fibers (dc-TDFs).
• The use of dc-TDF effectively mitigated long-wavelength amplified spontaneous emission (ASE).
• The developed all-fiber laser offers a promising solution for high-power 1.76-μm light generation.