Fig. 1. Absorption and emission spectra. (a) Absorption spectra of Er(DBTTA)₃(DBFDPO) powder, Er(DBTTA)₃(DBFDPO)-doped PMMA film, and ErCl₃·6H₂O powder under room temperature; (b) photoluminescence spectrum of Er(DBTTA)₃(DBFDPO)-doped PMMA film under 365 nm excitation

Fig. 2. Intramolecular energy transfer mechanism among organic ligands DBTTA, DBFDPO, and Er³⁺ ions

Fig. 3. Device characterization results. (a) Structural diagram of polymer optical waveguide amplifier based on principle of evanescent-wave amplification; (b) SEM image of waveguide cross section with optical field distribution simulated using COMSOL and near-field spot shown in inset; (c) AFM image of Er(DBTTA)₃(DBFDPO)/PMMA polymer film

Fig. 4. Schematic of gain measurement system of organic EDWA with LED vertical top-pumping method

Fig. 5. Measurement results. (a) Relationship between output signal intensity and pump power; (b) relationship between relative gain and pump power with an input signal power of 1.8 μW; (c) relationship between relative gain and input signal power when pump power of 365 nm LED is fixed at 462 mW and signal power increases from 1.8 μW to 203.5 μW