Ridged LiNbO3 modulators fabricated by a novel oxygen-ion implant/wet-etch technique

This paper demonstrates a new ion implantation and wet-etch technique for fabricating high-quality ridged optical waveguides for high-speed LiNbO₃-based optical modulators. In addition, the paper demonstrates the fabrication of optical waveguide ridges >3 μm in height with 90°, and even re-entrant sidewall angles for the first time. The modeling used indicates that 90° (and re-entrant) sidewall ridges can reduce the required modulator drive voltage by 10-20% over modulators with conventional trapezoidal ridge profiles fabricated with reactive ion etching. 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 is fabricated 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.