Research of broadband waveguide amplifiers based on long-period waveguide grating and multilayer medium thin film

A broadband waveguide amplifier based on long-period waveguide grating and multilayer medium thin film filter is proposed. The long-period waveguide grating is directly written in the Er-Yb codoped phosphate glass waveguide by using UV-written technology and the multilayer medium thin film is coated on the output interface of the waveguide. The light transmission characteristics of the proposed filter are analyzed theoretically. The effects of the transmission spectra of the filter on the flattening gain spectrum of Er-Yb codoped phosphate glass waveguide amplifier are discussed. It's demonstrated that the flatness of below 1dB is achieved over a bandwidth of similar to 30nm.