Contact electrode method for bulk periodically poled LiNbO₃

Abstract

Over the past few years, there has been increasing interest in the use of quasi-phase-matched (QPM) nonlinear crystals, which permit noncritical-phase-matching for any wavelengths in the transparency range of the crystal, and have the advantage of using the largest component of the nonlinear susceptibility tensor, one that is not available in birefringent phase matching without walk-off problems. QPM can be achieved by an appropriate periodic modulation of the nonlinear coefficient, which corresponds to periodic domain reversal in ferroelectric materials. In particular, the application of QPM to bulk nonlinear optics has been revolutionised by the emergence of electric field poling techniques for patterning the domain structure of ferroelectric and polar crystals. In all the reported fabrication processes the periodic electrode (consisting of resist and/or metal layers) has been fabricated on the surface of the crystal substrates by conventional photolithography.We report here a new fabrication process for PPLN - the contact electrode method (CEM) - in which the periodic electrode is pressed onto one of the substrate surfaces with a uniform electrode on the other. CEM does not need any photolithographic processes on the substrate surface which may lead to greatly reduced fabrication cost. Furthermore, CEM would be applicable for fabrications of periodically poled glass fiber