Creating poled aluminum gallium arsenide usually requires wafer bonding, which complicates the fabrication process and increases the cost. The final devices, however, show high waveguide losses due to scattering. By intentionally misorienting the wafer surface, the researchers can favor one orientation over another. Then the surface is patterned and etched to resembled a crenellation. The interface between the two phases grows vertically through the material.
Defects occurring along the interfaces cause a corrugated surface.
They believe that the major cause of the loss is scattering from the corrugations. The group has been learning how to reduce the defects, and thus the corrugation in the devices. Further work will provide more accurate measurements of the linear and nonlinear properties of these waveguide devices. Yvonne Carts-Powell, based in Boston, writes about optoelectronics and the Internet.