Propagating modes in gain-guided optical fibers

Area of Science:

• Optics and Photonics
• Laser Physics
• Materials Science

Background:

• Conventional optical fibers rely on index guiding for light propagation.
• High-power single-mode fiber lasers require advanced guiding mechanisms.
• Gain-guiding effects offer potential advantages over traditional index guiding.

Purpose of the Study:

• To investigate optical fibers where gain-guiding is significant or dominant.
• To derive propagation characteristics for mixed gain and index guiding in waveguides.
• To introduce a new parameter for characterizing these advanced optical fibers.

Main Methods:

• Derivation of propagation characteristics for symmetrical slab waveguides.
• Analysis of cylindrical optical fibers with mixed gain and index guiding.
• Assumption of a single uniform transverse profile for gain and refractive-index steps.
• Introduction of a complex-valued v-squared parameter for characterization.

Main Results:

• Formulation of propagation characteristics for optical fibers with mixed guiding.
• Demonstration that a complex-valued v-squared parameter accurately describes these fibers.
• Comparison with conventional real-valued v parameter used for index-guided fibers.

Conclusions:

• Optical fibers with significant gain-guiding are promising for high-power lasers.
• The complex-valued v-squared parameter provides a suitable framework for analyzing such fibers.
• This approach advances the understanding and design of next-generation fiber lasers.