Scalable waveguide design for three-level operation in Neodymium doped fiber laser

Area of Science:

• Optics and Photonics
• Laser Physics
• Materials Science

Background:

• Neodymium-doped fiber lasers are crucial for various applications.
• Previous fiber laser designs faced limitations in power scaling and spectral purity.
• The ⁴F_3/2→⁴I_9/2 transition offers potential for visible light generation but is challenged by stronger transitions.

Purpose of the Study:

• To construct and characterize a double-clad neodymium-doped fiber laser operating on the ⁴F_3/2→⁴I_9/2 transition.
• To develop a novel waveguide for spectral filtering to suppress competing transitions and enable power scaling.
• To investigate the potential for higher output power through optimized pumping strategies.

Main Methods:

• Fabrication of a double-clad neodymium-doped fiber laser.
• Pumping the laser at 808 nm and subsequently with combined 808 nm and 880 nm sources.
• Development of an all-solid micro-structured optical fiber waveguide with resonant inclusions for spectral filtering.
• Characterization of output power, slope efficiency, and spectral properties.

Main Results:

• Achieved 11.5 W output at 925 nm with 55% slope efficiency using 808 nm pumping.
• Reached 27 W output power with dual-wavelength pumping (808 nm and 880 nm), limited by available pump power.
• Developed a waveguide demonstrating strong spectral suppression of the ⁴F_3/2→⁴I_11/2 transition.
• The waveguide design supports large mode areas, overcoming limitations of previous approaches.

Conclusions:

• The constructed neodymium-doped fiber laser demonstrates high efficiency for the ⁴F_3/2→⁴I_9/2 transition.
• The novel spectral filtering waveguide is key to suppressing unwanted transitions and enabling significant power scaling.
• This approach paves the way for higher-power fiber laser systems at 925 nm and potentially other wavelengths.