Phase conjugated master oscillator fiber power amplifier

High-power narrow-linewidth fiber lasers are fundamentally limited by stimulated Brillouin scattering (SBS), which constrains further power scaling while maintaining spectral linewidth. Traditional mitigation techniques, such as active phase modulation, often introduce trade-offs among complexity, cost, and spectral brightness. In this study, we propose and experimentally demonstrate a novel all-optical approach for spectral linewidth manipulation and SBS suppression using optical phase conjugation (OPC). By leveraging nonlinear spectral broadening followed by phase conjugation, this method enables sophisticated linewidth narrowing in fiber amplifier, resulting in narrow linewidth output and enhanced SBS threshold. Using a low-cost fiber oscillator as the seed source, we achieve a spectral compression ratio exceeding 3 times. This method not only eliminates the need for complex electro-optic modulation systems but also provides a pathway toward simpler, high-brightness fiber laser systems. Our findings underscore the viability of OPC as a transformative tool for nonlinearity management and power scaling in high-performance fiber laser architectures.