Progress in ferroelectric domain engineering at the micro / nanoscale

Ferroelectric materials such as lithium niobate (LN) or lithium tantalate (LT) are examples of an extremely versatile class of optical crystals. In bulk single crystal, single domain format, these crystalline hosts find numerous applications in nonlinear optics, optical storage, photorefraction, surface acoustic wave devices, optical waveguides, piezoelectric and pyroelectric devices and electro-optic modulation. Single domain crystals can be subsequently engineered via spatially selective poling to yield domain structures whose size can lie in the region of a few tens of µm to sub-µm, for applications and device fabrication that are impossible to implement in single domain geometry. This paper discusses our progress to date in micro- and nanostructuring of such materials, for applications in nonlinear optics, switching and deflection, and 3-dimensional sculpting for possible MEMS use, The techniques and benefits are discussed of using both light-assisted and direct optical poling for achieving controllable domains that can be irregular or periodic, bulk or surface, at sizes that approach the 100 nm scale. For surface inversion, domain features can be produced that lack the otherwise characteristic crystal symmetry imposed hexagonal shapes observed in conventional electric field poling