Power scaling laser diodes using phase conjugates master oscillator power amplifier systems

The authors have performed experimental and theoretical investigations on scaling semiconductor lasers to higher powers with good beam quality and single-frequency operation by the use of large-area diode amplifiers and optical phase conjugation. They have demonstrated diffraction-limited single-frequency performance from a large aperture in a phase-conjugate master oscillator power amplifier (PC MOPA) geometry. They describe experimental results on a four-pass amplifier geometry that more readily allows efficient heat sinking and scaling to multiple ampilfier elements in two dimensions. A broad area is used instead of a striped amplifier element to eliminate sidelobes in the far field. The geometry used in the four-pass PC MOPA experiments is described. Amplifier near-field intensity after two passes, the four-pass far-field pattern, and the optical spectrum are shown. The authors have developed a wave-optical model to investigate the behavior of the four-pass PC MOPA and have shown the conditions under which the phase conjugator can correct for or prevent the formation of filaments in the power amplifier.