Strong radiation force induced in two-dimensional photonic crystal slab cavities

Radiation force induced by an electromagnetic field stored in a two-dimensional photonic crystal slab is examined. We considered two different types of photonic crystal cavities, namely, double-layer slab cavity structures and air-slot cavity structures. With double-layer structures, induced force is attractive or repulsive depending on the spatial symmetry of the stored electromagnetic field profile. For air-slot structures, we showed that a horizontal attractive force is induced between slabs, and it could be stronger than that for double-layer structures in the case considered here. The induced force on a photonic crystal slab is so strong that it can be detected experimentally with the microelectromechanical systems technique. A simple physical model based on a coupled-resonator well describes these results.

Figure 1

Double-layer of five-hole defect photonic crystal cavity. The cavity consists of five missing holes with shifted side holes. Two slabs are located with a separation $d$. The thickness of each slab $t$ is 105 nm.

Figure 2

(Color online) Mode: top and side views of DL-PCS cavity modes. (a) is the even mode and (b) is the odd mode in the vertical direction.

Figure 3

(Color online) $Q$ factor of double-layer cavities as a function of the separation of the two layers. The solid and open circles indicate the even and odd modes, respectively.

Figure 4

(Color online) Resonant wavelength of double-layer cavities as a function of the separation of the two layers. The solid and open circles indicate the even and odd modes, respectively. The horizontal dotted line around 1300 nm indicates the resonant mode of an isolated slab cavity.

Figure 5

(Color online) Radiation force of even mode. The solid circles are energy-momentum tensor results.

Figure 6

(Color online) Radiation force of odd mode obtained with Eqs. (1, 2). The open circles are EMT results including the effect of the field momentum term.

Figure 7

(Color online) Air-slot cavity. The colored side holes have the same radius with their position shifted outward.

Figure 8

(Color online) Calculated resonant wavelength of air-slot cavities (red) and of DL-PCS cavities (blue).

Figure 9

(Color online) $T_{xx}$ and $T_{xy}$ components of EM tensor.

Figure 10

(Color online) Radiation force of air-slot cavities compared with that of double-layer cavities.

Figure 11

(Color online) (a) is a schematic of the Fabry-Perot resonator model, which has a cavity between half-infinite dielectric media. (b) is a schematic of a coupled cavity model where two cavities couple through an evanescent field.

Figure 12

(Color online) Resonant wavelength calculation with Fabry-Perot (dashed line) and coupled-resonator (solid line) models.

Figure 13

(Color online) Radiation force calculation with Fabry-Perot (dashed line) and coupled-resonator (solid line) models.