Direct-write method for domain inversion patterns in LiNbO3

We have developed a technique to directly write stable ferroelectric domain patterns into lithium niobate crystals using visible light from an argon laser tightly focused to a diffraction limited spot in a confocal luminescence microscope. The patterns produced exhibit feature sizes down to 2 μm and show very little strain. The coercive field was reduced by as much as 30%. From the dynamics of the process, we attribute the reduction in coercive field to space charge fields produced by photoionization of defects. We have ruled out the possibility that the reduction in coercive field is simply a result of increased temperature by making local temperature measurements using the Stokes/anti-Stokes intensity ratio in confocal Raman measurements.