Fabrication of 2D sub-micron structures in lithium niobate for photonic crystal applications

Year: 2005

Authors: Grilli S., Ferraro P., Sansone L., Tiribilli B., Vassalli M., De Natale P.

Autors Affiliation: Istituto Nazionale di Ottica Applicata (INOA), Sez. di Napoli, Via Campi Flegrei 34, 80078 Pozzuoli (NA), Italy;
Istituto dei Sistemi Complessi – CNR, Largo E. Fermi 6, 50125 Firenze, Italy

Abstract: 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 shortpitch
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, electrooptically modulated Bragg gratings. Moreover moiré 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.

Journal/Review: PROCEEDINGS OF SPIE

Volume: 5931      Pages from: 593107-1  to: 593107-9

KeyWords: lithium niobate; atomic force microscopy;