Efficient Er:Ti:LiNbO3 ridge waveguide amplifier by patterning As2S3 layer

Abstract

In this study, the effect of As2S3 waveguide layer on propagation gain for Er:Ti:LiNbO3 ridge waveguide amplifiers is investigated. In comparison with a typical titanium in-diffused channel waveguide, the three side Erbium in-diffusion of a 6 μm wide ridge waveguide and the better light confinement has improved the overlap between Er concentration and guided mode profiles up to 2.58 times. Our simulation demonstrates that by purposely adjusting the thickness of the three side As2S3 layer it is possible to pull the guided mode towards the ridge/air interface where Er concentration is higher. Consequently in this new configuration by taking advantage of the high refractive index As2S3 layer and mode de-shaping, the overlap relative to a ridge free of As2S3 layer has increased by 1.5 times thereby gain coefficient has been improved from 3.2 to 4.28 dB/cm at a coupled pump power of 200 mW. In comparison with a typical Ti channel waveguide amplifier, the relative overlap has increased by 3.88 times resulting in noticeable gain improvement from 0.65 to 4.28 dB/cm under the same Er diffusion conditions.