Polarization-independent broadband beam combining grating with over 98% measured diffraction efficiency from 1023 to 1080 nm

We report a grating solution for achieving broadband and polarization-independent properties that brings a laser combining system to much higher power levels. The grating, with a high-refractive-index-contrast bilayer ridge, was designed and successfully fabricated based on high-power laser coatings, lithography, and ion-beam etching technology. The measured -1st order non-polarized reflective diffraction efficiency of the grating exceeds 98% over the wavelength range of 1.023-1.08 μm, and the highest value is 99.15%.