Guided-wave frequency doubling in surface periodically poled lithium   niobate: competing effects
  We carried out second-harmonic generation in quasi-phase-matched \alpha-phase lithium niobate channel waveguides realized by proton exchange and surface periodic poling. Owing to a limited ferroelectric domain depth, we could observe the interplay between second-harmonic generation and self-phase modulation due to cascading and cubic effects, resulting in a nonlinear resonance shift. Data reduction allowed us to evaluate both the quadratic nonlinearity in the near infrared as well as the depth of the uninverted domains. 
Salvatore Stivala, Alessia Pasquazi, Lorenzo Colace, Gaetano Assanto,   Alessandro C. Busacca, Matteo Cherchi, Stefano Riva-...
physics.optics