High-gain optical amplification in a femtosecond laser inscribed Er³+-Yb³ ⁺ co-doped phosphate glass waveguide

In integrated photonics, erbium-doped waveguide amplifiers can effectively amplify weak optical signals, making high-efficiency waveguide amplifiers particularly crucial for enhanced power compensation. To date, various material platforms have been employed to realize on-chip waveguide amplifiers. Erbium-doped glass, as a promising optical platform, offers the potential for fabricating high-efficiency waveguide amplifiers. Herein, we demonstrate a waveguide amplifier fabricated by femtosecond laser direct writing in an Er³⁺-Yb³⁺ co-doped phosphate glass. The device achieves a remarkably low propagation loss of 1.84 dB/cm at 1550 nm. An internal net gain of 10.31 dB was obtained at a pump power of 350 mW for a waveguide length of 0.6 cm. Notably, the amplifier exhibits broadband signal enhancement covering the C-band, from 1510 nm to 1570 nm. This work has significant implications for the further development of integrated photonic devices.