Effect of Ion Beam-Assisted Deposition on the End Pumping and Outer Coupler Filters of a Laser Fiber

Abstract

Fiber lasers are powerful tools for metal processing. Fiber Bragg gratings at the ends of the fiber play an important role as a fully reflective mirror and light modulator for a specific wavelength. The common methods for the manufacture of fiber Bragg grating involve expensive ultraviolet lithography instruments and environmentally harmful chemicals to prepare the mask. A film coating method is proposed to prepare both end pumping and outer coupler ends of a fiber to function similar to a fiber Bragg grating. An electron gun, along with ion beam-assisted deposition (IAD), was used to produce end filters for end pumping and the outer coupler filter devices of a fiber used in a fiber laser. The optical performance is consistent with the calculated simulation results. Scanning electron microscopy results reveal a dense multilayer structure with distinct and unambiguous interfaces in the coated film using the IAD process while that without IAD is loose and pulverized structure. The film designed with electrical field reduction on the surface produced by the IAD process exhibits a higher laser damage threshold. The coated films produced by electron gun deposition with the aid of IAD provide an alternative method for end filters in the fiber of a fiber laser.