Measurement of enhanced radiation force on a parallel metallic-plate system in the microwave regime

We measure the force exerted by microwave radiation on a centimeter-sized parallel-plate metallic resonant unit. By varying the ambient environment, we distinguish carefully between the direct radiation force and the indirect photothermal component. At the microwave resonance, the former is measured quantitatively to be 100 times larger than the conventional radiation force. Furthermore, the enhanced radiation force tends to increase the separation of the plates. Both the direction and the magnitude of the measured force agree well with numerical calculations.

Strong light-induced negative optical pressure arising from kinetic energy of conduction electrons in plasmon-type cavities

We found that very strong negative optical pressure can be induced in plasmonic cavities by LC resonance. This interesting effect could be described qualitatively by a Lagrangian model which shows that the negative optical pressure is driven by the internal inductance and the kinetic energy of the conduction electrons. If the metal is replaced by perfect conductors, the optical pressure becomes much smaller and positive.

Optical transmission through double-layer, laterally shifted metallic subwavelength hole arrays

We measure the transmission of IR radiation through double-layer metal films with periodic arrays of subwavelength holes. When the two metal films are placed in sufficiently close proximity, two types of transmission resonances emerge. For the surface plasmon mode, the electromagnetic field is concentrated on the outer surface of the entire metallic layer stack. In contrast, for the guided mode, the field is confined to the gap between the two metal layers. Our measurements indicate that, as the two layers are laterally shifted from perfect alignment, the peak transmission frequency of the guided mode decreases significantly, while that of the surface plasmon mode remains largely unchanged, in agreement with numerical calculations.