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

We demonstrate a new ion implantation 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 >3 mm in height with 90°, and even reentrant, sidewall angles for the first time. Our modeling indicates that 90° (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.