Five-mode erbium-doped waveguide amplifiers with low differential modal gain

Abstract

In this work, a five-mode erbium-doped waveguide amplifier with low differential modal gain (DMG) is first proposed. A novel, to the best of our knowledge, gain equalization scheme for synergistic reconfiguration of refractive index and concentration doping is adopted to equalize the modal gains based on the dual-layer ring core structure. NaYF4:5%Gd3+,20%Yb3+,2%Er3+@NaYF4 nanoparticles are synthesized by annealing treatment to improve the emission spectral properties and the concentration doped in a host core material. Leveraging the genetic algorithm and the minimization algorithm, the distributions of refractive index and layered doping are optimized. The high-precision alignment technology is presented to fabricate the devices. The crosstalk, near-field light spots, and loss and gain performances of the device are characterized. With only backward pumping of LP01 at a power of 150 mW, an average gain of 9.68 dB at 1550 nm with a DMG of 0.76 dB for five signal modes without distortion is achieved. This achievement establishes the foundation for enhancements in system data transmission capacity and integration scale.