Nested-ring doping for highly efficient 1907  nm short-wavelength cladding-pumped thulium fiber lasers.

Area of Science:

• Fiber laser technology
• Optoelectronics
• Materials science

Background:

• Cladding-pumped thulium-doped fiber lasers struggle with efficiency below 1950 nm due to three-level system effects and competing longer wavelength emissions.
• Achieving high-power, scalable output at shorter wavelengths (<1950 nm) remains a significant challenge in fiber laser development.

Purpose of the Study:

• To develop a novel fiber laser design for efficient, high-power operation at short wavelengths (<1950 nm).
• To overcome the limitations of traditional fiber designs in this spectral region.

Main Methods:

• A nested-ring fiber design was developed, embedding a highly doped thulium (Tm) ring within a larger undoped core.
• The fiber was specifically engineered to optimize short-wavelength emission.

Main Results:

• The nested-ring thulium fiber laser generated 62 W of single-mode output at 1907 nm.
• Slope efficiencies of up to 65% (with respect to launched pump power) and 70% (with respect to absorbed pump power) were achieved.

Conclusions:

• The demonstrated nested-ring fiber design enables highly efficient and power-scalable thulium-doped fiber laser operation below 1950 nm.
• This advancement addresses key challenges in short-wavelength fiber laser generation.