Spectral and temporal evolution in phase-conjugated master oscillator fiber power amplifier.

Spectral compression performance in a phase-conjugated master oscillator power amplifier is numerically investigated using the nonlinear Schrödinger equation. The conjugated wave of a nonlinearly spectrum-broadened laser is injected as a seed source into a fiber amplifier, in which the spectral linewidth is simultaneously compressed during power amplification. As a result, stimulated Brillouin scattering in the fiber amplifier can be effectively suppressed. Comprehensive spectral and temporal analyses reveal the intrinsic nonlinear dynamics, demonstrating how the coupling between dispersion and nonlinearity alters the frequency-time profile and feeds back onto their joint dynamics. Building on these physical insights, concrete optimization strategies for linewidth compression are proposed. Requiring no electro-optic modulators, this approach offers a promising pathway for scaling narrow-linewidth fiber lasers and provides fresh perspectives on nonlinearity management in high-power laser systems.