Design and fabrication of a superior nonpolarizing long-wavelength pass edge filter applied in laser beam combining technology

The wavelength combining technique has been widely used to increase the power scaling of lasers. The edge filter, which is nonpolarizing for wavelength, has proven to be a critical component for the combining process, and should have high spectral efficiency, high laser induced damage threshold, and excellent thermal stability. Here, we design a superior nonpolarizing long-wavelength pass edge filter using a novel depolarized initial film structure based on a tuned Fabry–Perot interference filter. The coating fabricated by electron beam evaporation can withstand ${130}\;{{\rm kW/cm}^2}$130kW/cm2 of continuous laser energy with high spectral efficiency at 45° and a small temperature rise.