Pump light leakage at coupler of side-pumped double-clad fiber laser with a novel dielectric-metal-dielectric sandwich structure

A multi-coupler side-pumped rare-earth-doped double-clad fiber laser with a novel dielectric-metal-dielectric(DMD) sandwich structure based on the theory of sub-wavelength diffraction grating is presented. A rigorous electromagnetic theory which considers the vectorial character of the light has been used to investigate and compute its pump light leakage at adjacent coupler for every coupled structure and it is found that pump light leakage is only 15.52% with a angle perpendicular to side of fiber. So this DMD sandwich structure can be applied to multi-point side-pump double-clad fiber laser effectively and the maximum coupling efficiency is greater than 80% after the second diffraction.