High brightness, quantum-defect-limited conversion efficiency in cladding-pumped Raman fiber amplifiers and...

Area of Science:

• Fiber optics
• Nonlinear optics
• Laser physics

Background:

• Cladding-pumped Raman fiber amplification offers potential for brightness enhancement of diode pump sources.
• Large clad-to-core diameter ratios are desirable but can lead to parasitic second-order Stokes generation.
• Parasitic effects limit conversion efficiency and brightness enhancement in conventional fiber designs.

Purpose of the Study:

• To theoretically investigate cladding-pumped Raman fiber amplification in a novel parameter space.
• To determine the upper limit of brightness enhancement as a function of diameter ratio.
• To propose strategies for overcoming existing limitations using depressed well core designs.

Main Methods:

• Detailed theoretical investigation using a coupled-wave formalism.
• Analysis of parasitic second-order Stokes wavelength generation.
• Modeling of pulsed cladding-pumped Raman fiber amplifier (CPRFA) and cw cladding-pumped Raman fiber laser (CPRFL) configurations.

Main Results:

• Identified an upper limit on brightness enhancement for conventionally guided fibers based on diameter ratio.
• Demonstrated that parasitic effects clamp achievable brightness enhancement.
• Proposed depressed well core designs as a strategy to overcome these limitations.

Conclusions:

• Depressed well core designs are crucial for achieving high conversion efficiency (>60%) and brightness enhancement (>1000).
• This research provides a pathway for advanced Raman fiber amplifiers and lasers.
• The findings unlock unexplored parameter spaces for high-power fiber optic sources.