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

A hybrid Si
₃
N
₄
-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 Si
₃
N
₄
strip. Benefiting from the low loss of the Si
₃
N
₄
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
cm
³
/sec using a simplified Er
³⁺
energy level model at a high Er concentration of 1.41 × 10
²¹
cm
^-3
and an Er
³⁺
emission cross section of 8.64 × 10
^-21
cm
²
.