We present S and P polarized measurements of artificial bianisotropic magnetic metamaterials with resonant behavior at infrared frequencies. These metamaterials consist of an array of micron sized (~40μm) copper rings fabricated upon a quartz substrate. Simulation of the reflectance is obtained through a combination of electromagnetic eigenmode simulation and Jones matrix analysis, and we find excellent agreement with the experimental data. It is shown that although the artificial magnetic materials do indeed exhibit a magnetic response, care must be taken to avoid an undesirable electric dipole resonance, due to lack of reflection symmetry in one orientation. The effects of bianisotropy on negative index are detailed and shown to be beneficial for certain configurations of the material parameters.
Increasingly, the demand to monitor structures in service is driving technology in new directions. Advances in many areas including novel sensor technologies afford new opportunities in structural health monitoring. We present efforts to develop structural composite materials which include networks of embedded sensors with decision-making capabilities that extend the functionality of the composite materials to be information-aware. The next generation of structural systems will include the capability to acquire, process, and if necessary respond to structural or other types of information. This work brings together many important developments over the last few years in several areas: developments in composites and the emergence of multifunctional composites, the emergence of a broad range of new sensors, smaller and lower power microelectronics with increased and multiple integrated functionality, and the emergence of algorithms that extract important structural health information from large data sets. This work seeks to leverage these individual advances by solving the challenges needed to integrate these into an information-aware composite structure. We present details of efforts to integrate and entrap connectorized microelectronic components within fiber/conductor braided bundles to minimize their impact as composite crack initiation centers. The bundles include conductors to transmit electric signals for power and communications. They are suitable for inclusion in woven composite fabrics or directly in the composite lay-up. The low-power electronic devices can operate on a multi-drop and point-to-point networks. Future directions include implementing in-network local processing, adding a greater range of sensors, and developing the composite processing techniques that allow sensor network integration.
Due to the recent experimental validations of left-handed metamaterials, negative refractive index has now become recognized as a new parameter space for the electromagnetic response of materials. Because materials with negative index behave quite differently than materials with positive index, many familiar electromagnetic phenomena must be reconsidered. Having established now the scientific basis of negative index, the effort of the community is turning toward the practical realization of both the predicted scientific phenomena and associated applications. In both of these pursuits, the ability to design, characterize and fabricate negative index materials is critical; we can consider the current status of negative refraction in some sense a materials issue, as our ability to demonstrate the predicted phenomena is linked to the quality of metamaterials we can produce. In this paper we consider several issues associated with the design and simulation of negative index metamaterials.
Nano gold particles interact strongly with visible light to excite the collaborative oscillation of conductive electrons within nano particles resulting in a surface plasmon resonance which makes them useful for various applications including bio-labeling. In this paper, we study the effect of particle sizes with particle plasmon resonant wavelength and the coupling between pair of elliptical metallic disks and ellipsoid particles by simulations and experiments. The red-shift resonant peak wavelength of coupled particles to that of single particle is due to particle plasmons near-field coupling. The shift decays is approximately exponentially with increasing particle spacing, and reaches zero when the gap between the two particles exceeds about 2.5 times the particle short axis length. It is also found that the exponential decay of peak shift with particle gap is size independent but shape dependent.
We present a detailed description of the apparatus and techniques that we have utilized in our experimental study of individual plas on resonant nanoparticles,along with a brief description of some major results. The apparatus consists of a spectroscopic system combined with a modified darkfield microscope, which enables the user to sequentially select individual resonant nanostructures in the microscopic field of view for spectroscopic study. Plasmon resonant
nanostructures scatter light elastically,and typically have very large scattering cross-sections at their resonant optical
wavelengths. In general, spectra can be obtained with acquisition times between .1 to 30 seconds,and color images can be captured using consumer digital color cameras. Spheres,tetrahedrons,and pentagonal platelets were fabricated using colloidal chemistry techniques. To produce highly anisotropic structures such as nanorods and "barbells", templates were used. Many of these nanostructures have been individually spectroscopically characterized,and their spectra correlated with their shape and size as determined by transmission electron icroscope (TEM). The unique shape,size,
composition,and dielectric surroundings of the individual plasmon resonant nanostructures determine their plasmon resonant behavior. We will show how the composition of the substrate on which the particles are immobilized and the dielectric of the surrounding medium have a significant effect on the plasmon resonance of the individual particles.
The large scattering cross section of plasmon resonant gold and silver nanoparticles functionalized with the appropriate ligand allows for sensitive and specific detection of nucleic acids and proteins. By varying the size, shape, and material morphology populations with a specific peak plasmon resonance can be prepared. By varying the order and length of plasmon resonant bar segment in a composite nanowire one can obtain a large number of particle populations. Distinct populations can be used for labels for multiplexing or as a platform for biological assays. An larger number of color populations can be obtained with composite nanowires that are fabricated with various lengths of silver, gold, or nickel segments. The order and length of the different plasmon resonance rod segments can be used to uniquely identify a rod population allowing for a large degree of multiplexing within a single sample.