Ultra-smooth LiNbO3 micro and nano structures for photonic applications

We report on two approaches to achieve ultra-smooth structures on lithium niobate (LiNbO3) substrates. The first method relies on ICP-RIE (inductively coupled-reactive ionic etching) or on RIE, and is exploited here for the fabrication of rods with smooth etched surfaces. A series of tests have been performed with fluorine gases. Nanometric rods with 200, 400 or 600nm diameters, with a periodicity of 400, 800 and 1200nm respectively and etched angles close to 68° for the RIE process and 75° for the ICP-RIE process have been fabricated. The second process is based on “optical grade dicing” and is dedicated to the fabrication of deep-etched ridge waveguides. First optical characterization results are reported. They show optical propagation losses value close to 0.1dB/cm.