Measuring Casimir Force And Electromagnetic Stress On Metamaterials Using Microelectromechanical Systems

Abstract
The coupling of electromagnetic radiation to mechanical motion is not only of fundamental interest but also relevant to practical applications. In this thesis, I will describe experiments investigating the local electromagnetic stress on a metamaterial unit. While it is well-known that the electromagnetic field is strongly concentrated at resonance and the total electromagnetic force can be strongly enhanced from the ordinary radiation force, here we show that the enhancement in the local electromagnetic stress is even larger. A general recipe for isolating the electromagnetic contribution from photo-thermal effects will also be described. In another effort, we investigate the strong geometry dependence of the Casimir force that arises from quantum fluctuations of the electromagnetic field. A monolithic measurement platform allows us to circumvent the alignment difficulties in Casimir force measurements. Since two silicon nanostructures can be aligned almost perfectly, we can measure the Casimir force even after their interpenetration. In our experiments, we mainly focused on two kinds of nanostructures. In the first T-shaped structure, we observed a non-monotonic Casimir force. A “Casimir spring” effect analog to the optical spring in the optomechanics is observed. The second structure consists of two interpenetrating gratings. It shows a Casimir force independent of the distance between the gratings. In such a structure, we measure a factor of > 500 deviations from the proximity force approximation, the strongest geometry dependence observed so far.