Until recently, it was widely believed among physicists that it was impossible to compress light below the so-called diffraction limit (see below), except when using metal nanoparticles, which unfortunately also absorb light. It therefore seemed impossible to compress light strongly in dielectric materials such as silicon, which are key materials in information technologies and come with the important advantage that they do not absorb light.
Click here for original story, Researchers compress light 12 times below the diffraction limit in a dielectric material
Source: Phys.org