Study about spectral beam combining with volume Bragg grating by means of Gaussian apodization technique

In order to study the suppression effect of side lobes of volume Bragg gratings(VBG) and the characteristics of the spectral beam combining with apodized VBG, the side-lobe of VBG was suppressed by means of Gaussian apodization. The diffraction characteristics of the Gaussian-apodized Bragg grating were analyzed based on the chain matrix method. Then the function of the combining efficiency with apodized grating was given, and the effect of apodized grating on the combining efficiency was analyzed. The results show that the peaks of the first four side-lobe are reduced from 73%,47%,31%,22% to 11%,20%,10%,7%, respectively. The combining efficiency decreases as the diffraction loss increases, when the number and the spectral width of combining beam are limited. Therefore, the diffraction loss between the combined beams is suppressed well after using the Gaussian-apodized grating that suppress the side-lobe of the VBG, and the combining efficiency increases.