Gain-Enhancement Strategy for C-Band Polymer Waveguide Amplifiers via Dual-Wavelength Pumping

Optical waveguide amplifiers are vital for on-chip loss compensation in photonic integrated circuits (PICs). Although C-band waveguide amplifiers have been widely studied, achieving high gain remains a considerable challenge. In this work, we present a gain-enhancement strategy based on core-shell nanoparticles (NPs) co-doped with multiple rare-earth ions (NaYbF4:Er3+, Ce3+@NaYF4:Yb3+, Nd3+). Efficient energy transfer from Nd3+ to Yb3+ ions significantly boosts the downconversion emission of Er3+ ions. When incorporated into a polymer waveguide amplifier, these NPs enable a maximum measured relative gain of 11.62 dB at 1535 nm in a 0.8 cm-long device under dual-wavelength (808 and 976 nm) pumping, which is 3.18 dB higher than the highest relative gain obtained under 976 nm single-wavelength pumping. This approach provides a route to enhanced C-band amplification and offers a strategy for designing compact, multi-wavelength-pumped photonic devices.