Asymmetry ridge structure fabrication and reactive ion etching of LiNbO₃

Ti-indiffused LiNbO₃ waveguides have been used for various high speed optical devices, such as modulators, switches and sensors, because of their electro-optic effect. In order to broaden the modulation bandwidth of an optical modulator above 10 GHz, both impedance matching and optical and RF phase velocity matching should be obtained at the high frequency range. This can be obtained by increasing the effective contact area of the CPW (co-planar waveguide) electrodes with air by means of LiNbO₃ substrate etching. We studied the properties of LiNbO₃ dry etching, in terms of the etching rate, etching angle and surface roughness, using a neutral loop discharge (NLD) plasma.