Reactive ion etching(RIE) of LiNbO_3(LN) in SF_6 plasma atmosphere was studied for optimizing the preparation conditions for LN ridge waveguides.The samples to be etched are Ti-diffused LN slab waveguides overlaid with a chromium film mask that has a Mach-Zehnder interferometer(MZI) array pattern.The experimental results indicate that the LN-etching rate(R_(LN)) and the Cr-etching rate(R_(Cr)) as well as the rate ratio R_(LN)/R_(Cr) increase with either increasing the radio-frequency(RF) power at a given SF_6 flow rate or increasing the SF_6 flow rate at a fixed RF power.The maximum values of R_(LN) = 43.2 nm/min and R_(LN)/R_(Cr) = 3.27 were achieved with 300 W RF power and 40 sccm SF_6 flow.When the SF_6 flow rate exceeds 40 sccm,an increase in the flow rate causes the etching rates and the rate ratio to decrease.The scanning electron microscope images of the LN ridge prepared after～20 min etching show that the ridge height is 680 nm and the sidewall slope angle is about 60°. Reactive ion etching (RIE) of LiNbO_3 (LN) in SF_6 plasma atmosphere was studied for optimizing the preparation conditions for LN ridge waveguides. The samples to be etched are Ti-diffused LN slab waveguides overlaid with a chromium film mask that has a Mach- The experimental results indicate that the LN-etching rate (R_ (LN)) and the Cr-etching rate (R_ (Cr)) as well as the rate ratio R_ (LN) / R_ ) increase with either increasing the radio-frequency (RF) power at a given SF_6 flow rate or increasing the SF_6 flow rate at a fixed RF power.The maximum values ​​of R_ (LN) = 43.2 nm / min and R_ (LN) / R Cr = 3.27 was achieved with 300 W RF power and 40 sccm SF_6 flow.When the SF_6 flow rate exceeds 40 sccm, an increase in the flow rate causes the etching rates and the rate ratio to decrease. The scanning electron microscope images of the LN ridge prepared after ~ 20 min etching show that ridge height is 680 nm and the sidewall slope angle is about 60 °.