High-gain polymer optical waveguide amplifiers based on core-shell NaYF₄/NaLuF₄: Yb³⁺, Er³⁺ NPs-PMMA covalent-linking...

Waveguide amplifiers have always been significant key components for optical communication. Unfortunately, the low concentration of rare earth ions doped in the host material and the inadequate optimization of the waveguide structure have been the common bottleneck limitations. Here, a novel material, NaYF₄/NaLuF₄: 20% Yb³⁺, 2% Er³⁺ nanoparticle-Polymeric Methyl Methacrylate covalent-linking nanocomposite, was synthesized. The concentrations of Er³⁺ and Yb³⁺ doping increased an order of magnitude. Under a 980 nm laser excitation, highly efficient emission at 1.53 μm was obtained. The characteristic parameters of the single mode waveguide were carefully designed and optimized by using a finite difference method. A formulized iteration method is presented for solving the rate equations and the propagation equations of the EYCDWA, and both the steady state behavior and the gain were numerically simulated. The optimal Er³⁺ and Yb³⁺ concentrations are 2.8 × 10²⁶ m^-3 and 2.8 × 10²⁷ m^-3, and the optimal waveguide length is 1.3 cm. Both theoretical and experimental results indicated that, for an input signal power of 0.1 mW and a pump power of 400 mW, a net gain of 15.1 dB at 1530 nm is demonstrated. This result is the highest gain ever reported in polymer-based waveguide amplifiers doped with inorganic Er³⁺-Yb³⁺ codoped nanocrystals.