Wet-etched ridge waveguides in y-cut lithium niobate

By the technique of nickel indiffusion proton exchange (NIPE) and the technique of buffered proton exchange (PE) melt, wet-etched ridge waveguides in y-cut LiNbO₃ are fabricated for the first time. The fabricated ridge waveguides have smooth surfaces and are good enough for low-loss waveguides. Moreover, a ridge waveguide Mach-Zehnder modulator in y-cut LiNbO₃ is fabricated. The measured half-wave voltage is about 30% lower than that of a conventional modulator. The wet-etched ridge waveguides in y-cut and z-cut substrates are also characterized for comparison