Deep periodic domain inversions in x-cut LiNbO3 and its use for second harmonic generation near 1.5μm

In this letter, we report the fabrication of deep x-cut periodically poled lithium niobate (PPLN) crystal. The technique relies on ridges performed by wet etching to improve poling field penetration into the substrate and, hence, to provide more depth to inverted domains. Based on this approach, domain inversions as deep as 6.5μm were achieved. As an application, reverse proton exchanged waveguides were fabricated on top of the PPLN to demonstrate efficient second harmonic generation in the near infrared. A conversion efficiency as high as 46%W−1cm−2 was measured near 1.5μm.