A switchable silicon waveguide demonstrated by scientists at Danmarks Tekniske Universitet in Lyngby, Denmark, points to the possibility of integrating electronics and photonics in monolithic components for computing and telecommunications applications. They presented their findings in the May 11 issue of Nature. The waveguide employs an amorphous Si3N4 straining layer to change the refractive index of the silicon waveguide by breaking the material’s crystal symmetry. The researchers note that the switching speed of the approach is not limited by charge mobility or recombination times, as in previous silicon-based optical modulators that operate by changing the carrier concentration through the application of current. To employ the strain-induced electro-optical effect for optical modulation, they propose replacing one leg of a silicon Mach-Zehnder interferometer with such a waveguide.