Hybrid ${\rm Si}_{3}{\rm N}_{4}\hbox {-}{\rm Er}/{\rm Yb}$ Silicate Waveguides for Amplifier Application

A hybrid Si₃N₄-Er/Yb silicate waveguide structure was fabricated by depositing 400-nm-thick Er/Yb silicate film on a 2.4-μm-wide and 250-nm-thick Si₃N₄ strip. Benefiting from the low loss of the Si₃N₄ materials, the propagation loss of the hybrid waveguide was as low as 3.2 ±0.3 dB/cm. A 3.1-dB signal enhancement was observed in a 5.9-mm-long waveguide under 1476-nm pumping of 372 mW. The optical gain was limited by the cooperative upconversion, which was calculated to be (3.0±1) × 10^-17 cm³/sec using a simplified Er³⁺ energy level model at a high Er concentration of 1.41 × 10²¹ cm^-3 and an Er³⁺ emission cross section of 8.64 × 10^-21 cm².