Spectral beam combining of Yb-doped fiber lasers with high efficiency

Spectral beam combining is a power scaling concept for fiber lasers, where several individual laser beams with different wavelengths are overlapped utilizing a dispersive element. We present a combination of three master-oscillator power-amplifier fiber laser systems to a total power of 153 W. Due to the employment of single-polarization low-nonlinearity photonic crystal fibers in the main amplification stages a combining efficiency as high as 95% has been realized. The measured beam quality of M2=1.2 for each laser does not decrease for the combined beam. Thus this setup provides excellent opportunities for brightness enhancement. Additional considerations for further increase in power are made.