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

Single-crystal congruent lithium niobate samples have been illuminated on the +z crystal face by pulsed ultraviolet laser wavelengths below (248 nm) and around (298-329 nm) the absorption edge. Following exposure, etching with hydrofluoric acid reveals highly regular precise domain-like features of widths ~150-300 nm, 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 ~2 micron. We envisage this direct optical poling technique as a viable route to precision domain-engineered structures for waveguide and other surface applications

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

Single-crystal congruent lithium niobate samples have been illuminated on the +z crystal face by pulsed ultraviolet laser wavelengths below (248 nm) and around (298-329 nm) the absorption edge. Following exposure, etching with hydrofluoric acid reveals highly regular precise domain-like features of widths ~150-300 nm, 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 ~2 micron. We envisage this direct optical poling technique as a viable route to precision domain-engineered structures for waveguide and other surface applications

Nano-scale ultraviolet laser-induced ferroelectric surface domains in lithium niobate

Microstructuring of ferroelectric domain patterns is necessary to achieve quasi-phase-matching (QPM) in nonlinear crystals for efficient frequency conversion. The preferred method for engineering the domain structure in lithium niobate is currently electric field poling, where a lithographically-defined electrode pattern on a z crystalline face delivers a large electric field in excess of the coercive field, forming a spatially selective domain-inverted pattern within the crystal

Ultraviolet laser induced sub-micron periodic domain formation in congruent undoped lithium niobate crystals

We report the formation of ordered sub-micron periodic surface domains on the -z face of congruent undoped lithium niobate single crystals induced by pulsed ultraviolet laser illumination of the sample faces under specific irradiation conditions. We demonstrate the utility of this simple light-induced technique for achieving periodic domain inversion and investigate the nature and spatial structure of these nano-domains by scanning force microscopy. We also demonstrate subsequent re-inversion of a small region of these light-induced nano-domains using scanning force microscopy

Light-induced domain engineering in ferroelectrics

Fabrication of periodically inverted domain patterns in ferroelectric materials such as lithium niobate has been widely researched for the realisation of applications as diverse as quasi-phase-matched (QPM) non-linear devices, electro-optic Bragg deflectors, photonic band-gap structures, and piezoelectric devices such as micro-resonators, atom traps and micro-cavities. In order to overcome the limitations associated with E-field poling, we have been investigating the feasibility of a relatively simple single-step technique, which exploits the interaction of intense laser light with ferroelectric lithium niobate to engineer domains at micron and sub-micron scale-lengths. Some light-assisted poling experiments which take advantage of the ultraviolet light-induced transient change in the coercive field of the illuminated ferroelectric material to transfer a patterned light distribution into an equivalent domain structure in bulk crystals have already been reported for lithium tantalate and lithium niobate crystals. In this letter we report a direct optical poling technique that employs pulsed ultraviolet laser light to induce surface domain inversion in undoped lithium niobate in a single step. We further characterize the laser modified domain manipulated crystals using differential chemical etching and scanning force microscopy (SFM)