Nonlinear Integrated Optics with Periodically Poled Waveguides in LiNbO3

The advent of the electric field poling method to fabricate periodically poled, ferroelectric, nonlinear optical materials resulted in a renaissance of nonlinear optics. Since then quasi-phase matching has been used for efficient wavelength conversion in devices like frequency doublers, difference frequency generators (DFG) and optical parametric oscillators (OPO). Periodically poled Lithium Niobate (PPLN) proved to be not only one of the best materials for nonlinear bulk optics, but also the most attractive and suitable substrate material for nonlinear integrated optics. It is commercially available as high quality mono crystalline wafer of a diameter of up to 5” and has large nonlinear coefficients. Moreover, the electric field assisted poling technique is compatible with the two most important waveguide fabrication methods – (annealed) proton exchange and Ti-indiffusion. The development of nonlinear integrated optical devices did not only result in a considerable inprovement of device efficiency and stability in comparison with bulk frequency converters; also all-optical ultrafast functions like time-domain multiplexing, polarisation conversion, switching and sampling could be demonstrated with significantly reduced power levels (see e.g. [1]).