Nanoscale surface domain formation on the +z face of lithium niobate by pulsed ultraviolet laser illumination

Abstract

Single-crystal congruent lithium niobate samples have been illuminated on the +z crystal face by pulsed ultraviolet laser wavelengths below (248nm) and around (298–329nm) the absorption edge. Following exposure, etching with hydrofluoric acid reveals highly regular precise domain-like features of widths ∼150–300nm, exhibiting distinct three-fold symmetry. Examination of illuminated unetched areas by scanning force microscopy shows a corresponding contrast in piezoelectric response. These observations indicate the formation of nanoscale ferroelectric surface domains, whose depth has been measured via focused ion beam milling to be ∼2μm. We envisage this direct optical poling technique as a viable route to precision domain-engineered structures for waveguide and other surface applications.