Abstract.We develop an approach to fabricate arbitrary ferroelectric domain patterns on lithium niobate film (30-50 μm thick) by applying a structured external field at room temperature. The fabricating method can be operated easily to reach 1 μm linewidth resolution. The ferroelectric domain inversion is stable and uniform. Nonlinear diffraction is generated when the fundamental wave pumps to film. Various nonlinear wavefronts are obtained such as the frequency converted optical vortex beam. A nonlinear holographic concept is proposed to explain the physical phenomena and guide the corresponding domain design. The applications in optical field manipulation and novel photonic states generation are discussed.
IntroductionLithium niobate (LN), a typical optoelectronic material, has been widely used in integrated optics due to its excellent nonlinear, electro-optic and acousto-optic properties [1][2][3][4]. Recently, the ferroelectric domain engineering on LN have attracted much attention because of the demand to realize nonlinear wave mixing process, including collinear and noncollinear situations in quasi-phase-matching (QPM) manners [5][6][7][8][9]. While it is difficult to carry out uniform micron linewidth ferroelectric domain inversion on typical 500-μm-thick LN crystal (the coercive field is about 21 kV/mm.) at room temperature as the result of the domain growth from +c facet to -c facet. At the same time, the domain structures will deteriorate soon for submicron LN film (540 nm thick) [10].With the development of domain engineering applications, ferroelectric domain structure with micron or sub-micron linewidth is desired [11][12][13][14]. Here we develop a method to fabricate arbitrary ferroelectric domain patterns on LN film (30-50μm thick) by applying a structured external field at room temperature [15][16]. The ferroelectric domain inversion is stable and uniform with 1 μm linewidth resolution.Based on the pattern poled LN film, it is convenient to observe nonlinear diffraction of vortex beam following the nonlinear holographic principle [8,17]. Furthermore, we can effectively tailor nonlinear wavefronts with designed ferroelectric domain through computer-generation holograms (CGH) [18][19][20]. Also, suitable domain structure could be flexibly introduced into LN for spontaneous parametric downconversion [21].