Controlling photonic structures using optical forces

A light punch The use of optical forces to manipulate small particles, including living cells, is an established technique. Until now though, it has proved difficult to manipulate the optical response of photonic structures in a controllable manner; this is because such large forces are required to induce appreciable changes in the geometry of the structure. Now a team from Cornell University has fabricated a resonant photonic silicon nitride structure in which the optical response can be efficiently statically controlled using relatively weak attractive and repulsive optical forces. A static mechanical deformation of up to 12 nanometres in the structure's geometry can be induced with just one milliwatt of optical power, raising the prospect of micro-optomechanical systems with novel and distinct functionalities. Optical forces can be used to manipulate small objects; for instance, in optical tweezers. However, it is challenging to manipulate the optical response of photonic structures using optical forces because of the large forces that are required to induce appreciable changes in the geometry of the structure. Here, a resonant structure made of silicon nitride is demonstrated whose optical response can be efficiently statically controlled using relatively weak attractive and repulsive optical forces. The use of optical forces to manipulate small objects is well known. Applications include the manipulation of living cells by optical tweezers 1 and optical cooling in atomic physics 2 . The miniaturization of optical systems (to the micro and nanoscale) has resulted in very compliant systems with masses of the order of nanograms, rendering them susceptible to optical forces 3 , 4 , 5 , 6 . Optical forces have been exploited to demonstrate chaotic quivering of microcavities 7 , optical cooling of mechanical modes 8 , 9 , 10 , 11 , actuation of a tapered-fibre waveguide and excitation of the mechanical modes of silicon nano-beams 12 , 13 . Despite recent progress in this field 14 , 15 , 16 , 17 , it is challenging to manipulate the optical response of photonic structures using optical forces; this is because of the large forces that are required to induce appreciable changes in the geometry of the structure. Here we implement a resonant structure whose optical response can be efficiently statically controlled using relatively weak attractive and repulsive optical forces. We demonstrate a static mechanical deformation of up to 20 nanometres in a silicon nitr