Effects of angle dispersion and fabrication errors of gratings on beam characteristics of spectral combining systems

Considering the beam divergence ,the angle dispersion and the fabrication errors of groove angle of the grating and using ray tracing method, the calculation model for the phase change of the laser beam obliquely incident on the grating has been built up. Then, making use of the diffraction integral method and the principle of incoherent superposition of laser beams, the analytical expression for the output intensity distribution of each emitter after passing through the spectral beam combining system has been derived. Finally, according to the intensity second-order moments method, the M2-factor of the combined beam has been calculated and the efffects of the angle dispersion and the fabrication errors of grating groove angle on the beam characterristics of the spectral combining system h