Efficient strategy to increase higher order inter-modal stability of a step index multimode fiber

Area of Science:

• Optical Fiber Technology
• Laser Physics
• Materials Science

Background:

• Large mode area (LMA) fibers are crucial for high-power lasers and amplifiers.
• Increased mode numbers in LMA fibers lead to susceptibility to mode coupling and reduced stability.
• Effective index difference (Δneff) is a key parameter for ensuring mode stability.

Purpose of the Study:

• To develop a novel method for enhancing mode stability in multimode fibers.
• To investigate the impact of doped concentric rings on the effective index difference between higher-order modes.
• To improve the performance of LMA fibers for high-power applications.

Main Methods:

• Introduction of doped concentric rings within the core of a multimode fiber.
• Optimization of the doping profile to increase the effective index difference (Δneff) between higher-order modes (LP18, LP09, LP19).
• Characterization of mode spacing and stability in the modified fiber design.

Main Results:

• Demonstrated a novel approach to enhance mode stability by increasing Δneff.
• Achieved over 35% increase in mode spacing between higher-order modes through optimized doping.
• Confirmed the correlation between modal effective index difference and mode stability.

Conclusions:

• Optimizing doping profiles in LMA fibers can significantly enhance mode spacing and stability.
• The proposed technique is scalable for improving mode spacing between various higher-order and antisymmetric modes.
• This method offers a pathway to more robust and stable high-power fiber lasers and amplifiers.