Process errors of dielectric gratings are divided into two classes: shape errors and dimension errors. A theoretical model of dielectric gratings with process errors has been proposed, and a beam propagation model of a transmission spectral-beam-combining (T-SBC) system has further been developed based on the process error model. Beam characteristics such as intensity distribution, beam width, beam quality, and combined power in T-SBC systems have been calculated and analyzed. The results show that shape errors make output power oscillated but have little impact on beam qualities of combined beams. The combined power for equal fill factor error yields the highest tolerance among shape errors. Dimension errors degrade both the power and beam quality of the combined beam. (c) 2019 Optical Society of America
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