Design a Hybrid WGA Based on Si3N4 and Li+‐Doped Er/Yb Silicate: Achieving High Gain in a Short Distance

Abstract Various erbium‐doped matrix materials are applied to achieve on‐chip waveguide amplifier (WGA), in order to fulfil the urgent requirements for compensating for losses in the integrated optical path. However, limited by the doping concentration of erbium ions in matrix materials, a long path of WGA is required for high gain. Here, a hybrid WGA is developed with silicon nitride as core and Li + ‐doped Er/Yb silicate (LEYS) as cladding, which achieves an insertion loss of 3.3 dB and high net gain of 9 dB in only 2‐mm‐long path, corresponding to an internal gain coefficient up to 6.15 dB mm −1 . Besides, the gain bandwidth covers the third telecommunication window of 1500–1600 nm. The highest gain coefficient for silicon‐based erbium planar waveguides (to the best of the knowledge) can be attributed to the using of gain medium and suitable waveguide design. The hybrid waveguide fully combines the advantages of high luminescence efficiency of LEYS and the characteristics of low loss silicon nitride, and it is further optimized through layout design. Furthermore, the fabrication of the WGA involves only photolithography and film deposition, avoiding ion implantation processes. Therefore, the proposed LEYS is an ideal gain medium to achieve highly compact on‐chip amplifiers.