Abstract— Periodic Poling of Lithium Niobate crystals (PPLN) by means of electric field has revealed the best technique for finely tailoring PPLN structures and parameters, which play a central role in many current researches in the field of nonlinear integrated optics. Besides the most studied technique of bulk poling, recently a novel technique where domain inversion occurs just in a surface layer using photoresist or silica masks has been devised and studied. This surface periodic poling (SPP) approach is best suited when light is confined in a thin surface guiding layer or stripe, as in the case of optical waveguide devices. Also, we found that SPP respect to bulk poling offers two orders of magnitude reduction on the scale of periodicity, so that even nanostructures can be obtained provided an high resolution holographic mask writing technique is adopted. We were able to demonstrate 200 nm domain size, and also good compatibility with alpha-phase proton exchange channel waveguide fabrication. Our first experiments on Lithium Tantalate have also shown that the SPP technology appears to be applicable to this crystal (SPPLT), whose properties can allow to overcome limitations such as optical damage or UV absorption still present in PPLN devices. Finally, the issue of SPP compatibility with proton exchange waveguide fabrication will be addressed. I. INTRODUCTION The fast growing of optical communication systems requires all optical networks featuring devices like all optical switches and wavelength converters. Optical parametric interactions in ferroelectric Lithium Niobate (LN) crystals have already been exploited for the realization of nonlinear devices suitable for all optical networks. In particular proton exchange (PE) waveguide technology together with periodic poling of ferroelectric domains of LN make available very efficient frequency doublers that rely on quasi phase matching (QPM) between the infrared (IR) pump and the generated second harmonic field [1]. Our attention has been focused on a new poling technique for LN crystals: the surface periodic poling of Lithium Niobate (SPPLN). With this technique only a tens of microns thick layer is poled and, on the other hand, it is possible to achieve very small periods with respect to standard bulk poling. In fact submicron poling has been demonstrated [2], [3], which is needed in some parametric interaction schemes, still unexplored due to technological limits. In order to get good conversion efficiencies high optical power densities are required along the whole path of nonlinear interaction between the input pump radiation and the generated second harmonic radiation. This is why it is convenient to fabricate the SPPLN structures on channel waveguides that confine optical power on an area comparable with the square of the optical wavelength and are not affected by diffraction problems when propagating over centimeters interaction lengths. The photolithographic mask for channel waveguide fabrication must withstand the proton exchange process, that requires dipping of the sample in an acid bath at high temperatures (300°C) [4]. For this purpose we have patterned silica films that we have deposited using the Ion Plating Plasma Assisted (IPPA) technique on the –Z face of the LN samples. Patterning has been done with a standard photolithographic technique, followed by an anisotropic dry plasma etching [5]. On the other hand the fabrication of periodic gratings for SPPLN requires a photolithographic mask featuring a good uniformity and high dielectric constant, capable of withstanding the high electric field that is applied during the poling process. Using IPPA deposited silica we have been able Surface Periodic Poling in Lithium Niobate and Lithium Tantalate A. Busacca, M. Cherchi, S. Riva Sanseverino Dipartimento Ingegneria Elettrica Elettronica e delle Telecomunicazioni, Università di Palermo Viale delle Scienze - 90128 Palermo, ITALY A. C. Cino, A. Parisi CRES - Centro per la Ricerca Elettronica in Sicilia Via Regione Siciliana 49 - 90046 Monreale (PA), ITALY G. Assanto, M. Cichocki, NooEL-Nonlinear Optics and OptoElectronics Lab. University Roma Tre Via della Vasca Navale 84, 00146 Roma, ITALY F. Caccavale, D. Calleyo, A. Morbiato SAES Getters S.p.A., Viale Italia, 77, 20020 Lainate (Milano) ITALY