Collectively enhanced optomechanical coupling in periodic arrays of scatterers

We acknowledge support from the Royal Commission for the Exhibition of 1851 (A.X.), the Austrian Science Fund (FWF) (Grant No. P24968-N27), an STSM grant from the COST Action MP1006 “Fundamental Problems in Quantum Physics” (C.G.), the EU CCQED and PICC projects, and the Danish Council for Independent Research under the Sapere Aude program (A.D.).We would also like to thank J. Bateman, K. Hammerer, I. D. Leroux, M. Paternostro, and H. Ritsch for fruitful discussions.