Generating high-quality beam in a multimode LD-pumped all-fiber Raman laser

Area of Science:

• Optics and Photonics
• Laser Technology
• Materials Science

Background:

• Developing high-power, high-beam-quality fiber lasers is crucial for various applications.
• Traditional laser designs often face limitations in power scaling and beam quality.
• Multimode fiber technology offers potential for higher power but typically suffers from poor beam quality.

Purpose of the Study:

• To demonstrate the first all-fiber Continuous Wave (CW) Raman laser utilizing multimode graded-index fiber.
• To achieve high-efficiency conversion of a multimode pump laser into a high-beam-quality output.
• To explore the integration of multimode fiber technologies for novel laser designs.

Main Methods:

• Directly pumping a multimode graded-index fiber with multimode fiber-coupled laser diodes.
• Utilizing the Raman clean-up effect within the fiber.
• Employing special fiber Bragg gratings for mode selection within the fiber core.

Main Results:

• Achieved high-efficiency conversion of a multimode pump (M²~26) at 915 nm to a high-quality output beam (M²~2.6) at 954 nm.
• Obtained approximately 50 W of output power.
• Demonstrated a slope efficiency of 67%.

Conclusions:

• The integration of multimode fiber technologies enables a new class of laser.
• This approach facilitates the development of high-power, high-beam-quality fiber lasers.
• The laser design allows for wavelength tunability based on available laser diodes (LDs).