Waveguide electro-optic modulation in micro-engineered LiNbO3

In this paper, after describing the basics of LiNbO3 based integrated electro-optic modulators, we will show how techniques such as etching, domain inversion and thin film processing can be used to realize new geometries which can take the performance to unprecedented levels. In particular we will review recent results on the use of domain inversion on a micron scale to improve the electro-optic response of LiNbO3 waveguide modulators in terms of bandwidth and driving voltage. These applications of domain inversion techniques might be even more important and commercially valuable than those in nonlinear optics ( e. g. quasi-phase-matched optical parametric devices). With respect to standard single-domain structures, larger bandwidths and lower driving voltages can be obtained, thus achieving figure of merits for the electro-optic response that are up to 50% larger. As a demonstration, a chirp-free modulator, having similar to 2 V switching voltage and bandwidth of 15 GHz, was fabricated by placing the waveguide arms of a Mach-Zehnder interferometer in opposite domain oriented regions. The modulator, as indicated by system measurements, could be driven in a single-drive configuration with inexpensive low-voltage drivers, e. g. SiGe based, typically used for electro-absorption devices.