Sub-micron ferroelectric domain engineering in liquid phase epitaxy LiNbO3 by direct-write e-beam techniques

In this paper, we report the effects of direct-write e-beam parameters on achieving sub-micron periodic domain structures in homoepitaxial liquid phase epitaxy (LPE) LiNbO3 thin films. We have studied the effects of the e-beam acceleration voltage, the areal dose, and the scanning speed on the domain structure regularity, and we have obtained optimal conditions for achieving improved structures. The most regular structures appear at acceleration voltages higher than 20 kV and areal dose ranges of 350-450 μC/cm2 with lower scanning speeds. Under these optimal conditions we have fabricated approximately 500 μm-long gratings with 1.1 μm periods consisting of ∼180 nm domains. By simulating the optical reflectance based on a transfer matrix analysis, we have shown that the grating has a reflectance close to that of a perfect grating, in spite of the existence of stitching errors. The results indicate that using this fabrication approach, a switchable Bragg filter for optical communications may be fabricated by direct-write e-beam sub-micron domain engineering in LPE LiNbO3.