We report a novel tunable nanophotonic device concept based on Mechanically Controlled Photonic Crystal (MCPC), which is comprised of a periodic array of high index dielectric material and a low index polymer. Tunability is achieved by applyingmiechanical force with nano-/micro-electron-mechanical system actuators. The mechanical stress induces changes in the periodicity of the photonic crystal, to which the photonic band strusture is extremely sensitive. This consequently produces tunability much greater than that achievable by electro-optic materials such as liquid crystal. Our theoretical investigations revealed that we could achieve dynamic beam steering over a wide range of angles up to 75° with only 10% mechanical stretching. We also predicted tunable sub-wavelength imaging in which we could tune the frequency response and focal length of negative index PC lens. For experimental demonstration, we fabricated the PC structures on Si-on-insulator substrates. Optical characterizations clearly showed the anticipated negative refraction in which the incident beam was refracted back to the side it was incident. The experimental demonstration of negative refraction at optical frequencies in a Si-based photonic crystal structure is a significant step toward the next-generation nanophotonics.
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