Ridged LiNbO3 Modulators Fabricated by a Novel Oxygen-Ion Implant/Wet-Etch Technique

We demonstrate a new ion implanatation and wet etch technique for fabricating high quality ridged optical waveguides for high-speed LiNbO3 based optical modulators. We demonstrate the fabrication of optical waveguide ridges > 3mum in height with 90deg, and reentrant, sidewall angles for the first time. Our modeling indicates that 90deg (and reentrant) sidewall ridges can reduce the required modulator drive voltage by 10% to 20% over modulators with conventional trapezoidal ridge profiles fabricated with reactive ion etching. We fabricate a 40 Gb/s modulator with a 30 GHz bandwidth, 5.1 V switching voltage at 1 GHz, and a 4.8 dB optical insertion loss using the ion implantation/wet etch process. Fabricated devices showed good stability against accelerated aging indicating that this process could be used for commercial purposes.