Abstract

Integrated optical functional elements like switches or frequency converters rely on materials with high nonlinear coefficients and broad band transparency. Such qualities are provided by the anisotropic crystal lithium niobate (LiNbO3). However, integration on a single crystal chip is hampered by the fact that different functional elements require different crystal cuts. Whereas modulators are best realised in x-cut crystals, efficient quasi-phase-matching (QPM) elements for frequency conversion are usually fabricated from periodically poled lithium niobate (PPLN) z-cut wafers [1]. Poling of x-cut wafers is only possible with surface electrodes. Hence, resulting poled domains extend only a few microns below the surface [2]. Here, we report ultrashort pulse laser inscription of QPM elements with cross-sections of 500 times 90 µm². The chosen approach is to periodically lower the nonlinear refractive index instead of reversing the domain.

© 2011 Optical Society of America