SNOM study of periodically poled ferroelectric domains in

The feasibility of forming periodic ferroelectric domain structures in ferroelectric crystals as: LiNbO3, LiTaO3 and Ba2NaNb5O15, has extended the range of application of these materials in the photonic field. In fact, it has been demonstrated the ability, using these ferroelectric periodic structures, to manufacture different non-linear optical devices as: optical super-lattices (OSLs), second harmonic generation (SHG), and difference frequency generation (DFG), as well as in new fields like squeezed light generation for optical communication and information processing [1,2]. These periodic ferroelectric structures can be achieved using different procedures: during the crystal growth by the “off centre Czochraski technique ” (OCCT), applying an external electric field (EF) or by electron beam injection method (EBI). The aim of this work is to study, in periodically poled LiNbO3 (CT), LiTaO3 (EF) and Ba2NaNb5O15 (CT) crystals, new phenomena arising from the interaction between laser propagating beams and refractive index singularities associated with the ferroelectric domains. For this purpose scanning near-field optical microscopy (SNOM) technique has been used [3]. The SNOM study has been combined with far field light diffraction experiments