Gain Improvement of $\hbox {Er-Ti:LiNbO}_{3}$ Waveguide Amplifier by an $\hbox {As}_{2}\hbox {S}_{3}$ <

A new configuration consisting of an arsenic trisulfide (As₂S₃) channel waveguide on top of an erbium (Er)-doped titanium-diffused x-cut lithium niobate (Er:Ti:LiNbO₃) waveguide has been investigated by simultaneous analytical expressions, numerical simulations, and experimentation. Both simulation and experimental results have shown that this structure can enhance the optical gain, as predicted by the analytical expressions. An As₂S₃ channel waveguide has been fabricated on top of a conventional Er:Ti:LiNbO₃ waveguide, where the higher refractive index As₂S₃ waveguide is used to pull the optical mode toward the substrate surface where the higher Er concentration yields an improved propagation gain. The relationship between the gain and As₂S₃ layer thickness has been evaluated, and the optimal As₂S₃ thickness was found by simulation and experimentation. Side integration was applied to reduce the extrapropagation loss caused by the titanium diffusion bump. The propagation gain has been improved from 1.1 to 2 dB/cm.