Ridge waveguide Mach-Zender modulators fabricated by a novel nickel-indiffused LiNbO3 self-aligned process

摘要

Abstract: Traditionally, there were two fabrication processes for LiNbO$-3$/ ridge waveguides, which were nickel (Ni) diffusion prior to PE wet etch, the DE process, and PE wet etch prior to Ni diffusion, the ED process. Though these processes have been optimized and are much better than the dry etch methods, further improvement is necessary. This is because the former easily result in unwanted planar waveguides flanking the ridge structures, while the latter requires relatively complicated process. In this paper, a novel self-aligned fabrication process for Ni:LiNbO$-3$/ ridge waveguides has been proposed. By using the self- aligned tri-layered structure composed of Ni/Ti/Si, the fabrication process is significantly simplified. Based on our observations, the deposited thickness of the self- aligned structure will determine the qualities of the ridge waveguides. Moreover, the novel self-aligned fabrication process was applied to fabricate a ridge waveguide Mach- Zehnder modulator. The measured half-wave voltage and extinction ratio were 20.5V and 12dB, and were 4.2V and 8dB. !15