Microstructuring in LiNbO3:: a route to MEMS devices in piezoelectric crystal media.

Ferroelectric materials such as LiNbO3 and LiTaO3 offer many potential advantages over silicon for MEMS structures and self-actuating miniature devices. These materials possess numerous useful intrinsic properties such as piezoelectricity, pyroelectric and electro-optic coefficients, enabling the construction of micron-scale cantilevers, membranes, tips and switches. So far however, reliable and accurate methods for machining and microstructuring LiNbO3 single crystals have been tacking. We have recently been exploring several such methods, which are sensitive to ferroelectric domain orientation. A sample that has been domain-engineered shows a large difference in etch characteristics: the +z face does not etch at all, whereas the -z face etches normally. Microstructured devices can be fabricated therefore, via spatially selective domain poling followed by etching. The extreme sensitivity of the etch process to domain orientation has enabled us to fabricate ridge waveguides for electro-optic modulator applications, alignment grooves for efficient fibre-pigtailing to LiNbO3 modulators, and microcantilevers using a novel technique of contact bonding of dissimilar ferroelectric hosts.