Photonic crystals are periodic structures that guide and trap light, whereas phononic crystals do the same for mechanical vibrations or sound. Oskar Painter and colleagues at the California Institute of Technology have now created optomechanical crystals that can act as both photonic and phononic crystals (Nature 462, 78–82; 2009). These crystals allow light and sound to be confined within a small region.

Painter and co-workers fabricated a ladder-like silicon nanobeam (left) that included a 'defect' in the form of a region at the centre of the beam where the spacing between the rungs in the ladder was reduced. The false-colour images (right) are simulations showing the first five mechanical modes of the system plus the fundamental optical mode; for each mode the results for the ideal rung spacing in the defect region are shown on the left and the results for the actual spacing are on the right.

Credit: © 2009 NPG