A new, all-optical technique for creating second-order nonlinear effects in materials that normally do not support them could lead to new options for creating these effects for optical computers, high-speed data processors, and bioimaging. A research group from Georgia Institute of Technology (Georgia Tech) developed the technique, using a red laser to create the nonlinear effects.
For their experiment, the researchers created an array of tiny plasmonic gold triangles on the surface of a centrosymmetric titanium dioxide (TiO2) slab in their lab. They illuminated the TiO2/gold structure with a pulse of red laser light. The laser beam acted as an optical switch, breaking the crystal symmetry of the material. The laser pulse, when fired at the array of gold triangles on the TiO2 slab, excited electrons, and this excitation briefly doubled the frequency of a beam from a second laser as it bounced off the amorphous TiO2 slab.