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Sub-micron period reversed domain patterns are fabricated in congruent LiNbO3 by using electric field overpoling. Slight wet etching of the domain engineered samples in HF solution generates surface relief structures faithfully reproducing the resist pattern geometries generated by holographic lithography. Moiré holographic lithography is also used to fabricate more complicated resist templates to be transferred onto the LiNbO3 substrates as surface structures. A wide variety of structures is presented and discussed. The preliminary results show the possibility to use the fabricated structures for the realization of photonic crystal devices such as Bragg gratings, micro-ring resonators, etc. for telecom applications.

We report on the fabrication and characterization of periodic nanoscale one- and two-dimensional surface structures in congruent 500 µm thick lithium niobate crystal samples. Structures with periods from 2 µm down to around 500 nm, lateral feature sizes down to 200 nm and depths compatible with conventional waveguide fabrication, have been obtained. Such structures are fabricated by applying polarity selective etching to periodically domain reversed samples obtained by electric field poling performed by overpoling regime. Holographic lithography is used to obtain sub-micron periodic insulating gratings to be used for selective ferroelectric domain reversal. The short pitch structures are attractive in a wide range of applications ranging from nonlinear optics, for short-wavelength conversion processes or backward second-harmonic generation, to the field of photonic crystals to fabricate novel tunable photonic crystal devices or electro-optically modulated Bragg gratings. Moreover moire beating effect is used in the photolithographic process to fabricate even more complex structures which could find applications in complicated photonic bandgap devices involving for example micro-ring resonators. In order to investigate the possibility to utilize these structures for photonic crystal applications, accurate topography characterization has been performed by using different techniques. Atomic force microscope provides high-resolution information about the lateral and depth feature size of the structures, while interferometric techniques, based on digital holography, have been used for wide field information about the homogeneity and periodicity of the structures.

We report on the fabrication and characterization of the first periodic sub-micron scale one- and two-dimensional surface structures in congruent 500 ?m thick lithium niobate crystal samples. Structures with periods from 2 ?m down to 500 nm, lateral feature sizes down to 200 nm and depths around 10 ?m, largely compatible with conventional waveguide fabrication, have been obtained. Such structures are fabricated by selective wet etching of ferroelectric domain engineered samples obtained by electric field poling performed at an overpoling regime. Holographic lithography is here used to obtain sub-micron periodic insulating gratings to be used for selective ferroelectric domain reversal. The short-pitch fabricated structures are attractive in a wide range of applications, such as nonlinear short-wavelength conversion processes, backward second-harmonic generation, fabrication of novel tunable photonic crystal (PC) devices, electro-optically modulated Bragg gratings. Moreover moire beating effect is used in the photolithographic process to fabricate even more complex structures which could find applications in complicated photonic bandgap devices involving for example micro-ring resonators. In order to investigate the possibility to utilize these structures for PC applications, accurate and complete topographic characterization has been performed by using different techniques. Atomic force microscope provides high-resolution information about the lateral and depth feature size of the structures. Interferometric techniques, based on digital holography, have been used for wide field information about the homogeneity and periodicity of the structures.