Showing papers by "Cheng Sun published in 2008"

Optical Negative Refraction in Bulk Metamaterials of Nanowires

Abstract: Negative refraction in metamaterials has generated great excitement in the scientific community. Although negative refraction has been realized in microwave and infrared by using metamaterials and by using two-dimensional waveguide structures, creation of a bulk metamaterial showing negative refraction at visible frequency has not been successful, mainly because of the significant resonance losses and fabrication difficulties. We report bulk metamaterials made of nanowires that show such negative refraction for all incident angles in the visible region. Moreover, the negative refraction occurs far from any resonance, resulting in a low-loss and a broad-band propagation at visible frequencies. These remarkable properties can substantially affect applications such as imaging, three-dimensional light manipulation, and optical communication.

Flying plasmonic lens in the near field for high-speed nanolithography

Abstract: The commercialization of nanoscale devices requires the development of high-throughput nanofabrication technologies that allow frequent design changes1,2. Maskless nanolithography3,4,5,6,7,8,9,10,11,12,13, including electron-beam and scanning-probe lithography, offers the desired flexibility but is limited by low throughput. Here, we report a new low-cost, high-throughput approach to maskless nanolithography that uses an array of plasmonic lenses that ‘flies’ above the surface to be patterned, concentrating short-wavelength surface plasmons into sub-100 nm spots. However, these nanoscale spots are only formed in the near field, which makes it very difficult to scan the array above the surface at high speed. To overcome this problem we have designed a self-spacing air bearing that can fly the array just 20 nm above a disk that is spinning at speeds of between 4 and 12 m s−1, and have experimentally demonstrated patterning with a linewidth of 80 nm. This low-cost nanofabrication scheme has the potential to achieve throughputs that are two to five orders of magnitude higher than other maskless techniques. Maskless nanolithography is a flexible nanofabrication technique but it suffers from low throughput. By developing a new approach that involves 'flying' an array of plasmonic lenses just 20 nm above a rotating surface, it is possible to increase throughput by several orders of magnitude.

Cloaking of matter waves.

Abstract: Invariant transformation for quantum mechanical systems is proposed. A cloaking of matter wave can be realized at given energy by designing the potential and effective mass of the matter waves in the cloaking region. The general conditions required for such a cloaking are determined and confirmed by both the wave and particle (classical) approaches. We show that it may be possible to construct such a cloaking system for cold atoms using optical lattices.

Plasmonic nearfield scanning probe with high transmission

Abstract: Nearfield scanning optical microscopy (NSOM) offers a practical means of optical imaging, optical sensing, and nanolithography at a resolution below the diffraction limit of the light. However, its applications are limited due to the strong attenuation of the light transmitted through the subwavelength aperture. To solve this problem, we report the development of plasmonic nearfield scanning optical microscope with an efficient nearfield focusing. By exciting surface plasmons, plasmonic NSOM probes are capable of confining light into a 100 nm spot. We show by nearfield lithography experiments that the intensity at the near field is at least one order stronger than the intensity obtained from the conventional NSOM probes under the same illumination condition. Such a high efficiency can enable plasmonic NSOM as a practical tool for nearfield lithography, data storage, cellular visualization, and many other applications requiring efficient transmission with high resolution.

Super-resolution imaging by random adsorbed molecule probes.

Abstract: Single molecule localization (SML) is a powerful tool to measure the position and trajectory of molecules in numerous systems, with nanometer accuracy. This technique has been recently utilized to overcome the diffraction limit in optical imaging. So far, super-resolution imaging by SML was demonstrated using photoactivable or photoswitchable fluorophores, as well as diffusive fluorophore probes in solution. All these methods, however, rely on special fluorophore or object properties. In this Letter, we propose and demonstrate a new super-resolution technique attainable for a bio/dielectric structure on a metal substrate. A sub-diffraction-limited image is obtained by randomly adsorbed fluorescent probe molecules on a liquid-solid interface, while the metal substrate, quenching the unwanted fluorescent signal, provides a significantly enhanced imaging contrast. As this approach does not use specific stain techniques, it can be readily applied to general dielectric objects, such as nanopatterned photoresist, inorganic nanowires, subcellular structures, etc.

Optical platform for simultaneously stimulating, manipulating, and probing multiple living cells in complex biological systems

Abstract: An optical platform and system for the simultaneous stimulation, manipulation and probing of multiple living cells in complex biological systems. The apparatus utilizes a spatiotemporal light modulator to expose a sample to pinpoints of light at selected times and wavelengths in two or three dimensional space and then detect the responses. In one embodiment, a spatiotemporal light modulator is optically coupled to a variable wavelength light source, a lens system and a system control unit with sample response sensors, wherein sample responses are detected after exposure to patterns of light in real time. Light patterns can be modulated in response to sample responses.

Negative Refraction In Bulk Anisotropic Metamaterials At Visible Frequency

Abstract: Bulk metamaterials consisting of silver wire arrays in alumina matrix was fabricated. Electro-magnetic (EM) waves propagating along the nanowires exhibit relatively low-loss negative refraction, at a broad band of frequency for all angles. Experimental results at 660nm and 780nm were shown with incident angle from −30 to 30 degree.

All Optical Platform for Parallel and Spatiotemporal Control of Neuronal Activity

Abstract: The platform is realized by delivering spatiotemporally complex optical stimuli through a digital micromirror spatiotemporal light modulator to cells expressing the light-activated channels, which have been labeled with a calcium dye to report of activity.

Cloaking of Cold Atoms

Abstract: Invariant transformation for quantum mechanical systems is proposed. We show that it may be possible to construct such a cloaking system for cold atoms using optical lattices.