Quasi-phase matching configurations

Nanometer scale domain configurations in fe bulk crystals pave the way for a new class of photonic devices. As an example, preliminary calculations show that a uv laser (A = 300 nm) based on second harmonic generation in LiTaC>3 crystal requires a periodic nanodomain superlattice with domain widths of around 700 nm. In addition, the current domain gratings in ferroelectric crystals are suitable only for quasi-phase-matched nonlinear interactions in the forward direction, where the pump and generated beams propagate in the same direction. Sub-micron ferroelectric domain gratings are the basis for a new family of devices based on backward nonlinear quasi-phase-matched optical interactions in which the generated beam travels in a reverse or another non-collinear direction to the incident beam. Non-collinear... 

In quasi-phase matching, the waves involved in the mixing process are not constantly locked in phase with each other. Instead, the crystal axis is flipped at regular intervals with period A (typically about 10-15 pm in length) such crystal stacks are called periodically poled. This configuration results in the polarization response of the crystal being shifted back in phase with the incident beam(s) by reversing the non-linear susceptibility periodically. 

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