Credit: © 2009 NPG

The optical forces from lasers are becoming widely used for moving, exciting or cooling nanostructures. Another potentially useful application of laser-induced forces would be to change the optical responses of photonic structures, but such work has proved to be difficult because it requires quite large forces to sufficiently change the structural geometry. Now, a team at Cornell University led by Michal Lipson have designed a device whose optical response changes significantly under relatively weak forces from a laser1.

The researchers used electron beam lithography to fabricate a wheel-like silicon nitride structure comprising two concentric rings 30 μm in diameter and just 190 nm thick, attached to a central pedestal by thin spokes. They used a pump laser to apply an optical force to the structure and a weak probe laser to monitor changes in the optical response of the cavity between the rings, which is very sensitive to the distance between rings.

Their results showed that a pumped laser with just 3 mW of power applied enough force to change the distance between the rings by up to 20 nm, corresponding to a large optical resonance shift in the cavity. This response implies that simlar devices could act as versatile components in complex optical circuits for future micromechanical systems.