30-watt level, 1.7 µm first-order Raman fiber laser with more than 99% spectral purity.

Area of Science:

• Laser Physics
• Fiber Optics
• Nonlinear Optics

Background:

• 1.7 μm lasers are crucial pump sources for efficient 3 μm mid-infrared laser generation.
• High-power and high-spectral-purity 1.7 μm fiber lasers are in demand for various applications.

Purpose of the Study:

• To develop a high-power, high-spectral-purity first-order Stokes Raman fiber laser operating at 1680 nm.
• To investigate the use of a broadband chirped fiber Bragg grating (CFBG) as a Raman cavity mirror to mitigate spectral mismatch.

Main Methods:

• A homemade 1565 nm master oscillator power amplifier (MOPA) was used as the pump source.
• A broadband CFBG with a 25.5 nm bandwidth was employed as the Raman cavity mirror.
• The laser's output power, spectral purity, slope efficiency, and power stability were characterized.

Main Results:

• Achieved an output power of 30.2 W at 1680 nm with a spectral purity of 99.2%.
• Obtained a slope efficiency of 72.9% relative to the launched pump power.
• Demonstrated excellent power stability with fluctuations below 1% over one hour.

Conclusions:

• This work presents a record high-power (30.2 W) first-order Stokes Raman fiber laser at 1.7 μm with >99% spectral purity.
• The developed laser offers a stable and power-scalable solution for generating high-power 1.7 μm lasers.
• The high spectral purity makes this laser a promising pump source for all-fiber integrated mid-infrared fiber lasers.