As demands for bandwidth continue to increase, telecommunication networks would greatly benefit from the development of broader-band amplifiers. The currently erbium doped fiber amplifiers are limited to amplification of approximately 100 nm bandwidth window. One method to increase the bandwidth of the fiber amplifier would be to incorporate multiple rare earths (REs) into a single fiber which exhibit emissions from ~1000-1800 nm. Unfortunately, energy transfer between rare earth ions typically results in quenching all but selected emissions negating this approach to potential ultra-broadband amplification. It would be ideal if one could take the individual spectra of an ion and place that ion into a host with no regard to other lanthanides that also are present in the host. This problem can be solved by using a composite material that utilizes nanoparticles to constrain different REs to individual particles thereby controlling or preventing energy transfer. In order to control energy transfer, RE doped LaF<sub>3</sub> nanocrystals were grown in an aqueous solution using a core/shell technique to constrain different rare earth into separate particles or shells within a single particle. Using these techniques, we show that energy transfer can be controlled.
The effects of period, geometry, and thickness on optically thick metal films perforated with subwavelength apertures have been an area of recent investigation, both experimentally and theoretically. It has been shown that the spectra of these films can be scaled proportionally to the period. Different geometries can change peak positions, and the thickness of a metal film can determine the degree of transmission for the entire spectrum. This tunability allows the positioning of a single peak to a wavelength of interest, but the position of all other peaks are dependent on the peak of interest and cannot be positioned independently. Further, the peak intensities are all related. This lack of individual control over specific peaks limits the future applicability of plasmonic films in optoelectronic and photonic devices. Transmission spectra that can be tuned by the polarization of the incident light can be fabricated with novel array structures. Further, control over the transmission spectra can be gained by using highly anisotropic apertures to modifying specific surface plasmon polariton modes and their associated peaks. Surface plasmon polariton modes that are not in the direct path of these anisotropic apertures are not significantly affected. This allows for controlled engineering of the intensity of peaks within the visible, greatly increasing the tailorability of the spectral characteristics of plasmonic films.
Organic - Inorganic matrix nano composites have been created using an acid catalyzed, tetraethyl orthosilicate-based sol- gel technique with SWNTs. By utilizing nanotubes functionalized with the dendron methyl 3,5- di(methyltrigycoloxy)benzylic alcohol, ultrasonication blending in the sol phase prior to gelation yields excellent dispersion characteristics of the nanotube phase. Further, glasses could easily be dried by heating to 600 degrees C yielding 80 percent of theoretical density wit little change in the nanotube content. These materials exhibited intrinsic Rayleigh scattering, suggesting near ideal dispersion. Nonlinear optical transmissivity was observed for 1064 and 532 nm light suggesting that the matrix has a strong broad band coupling to the optical field. Such composites allow for a host of applications based on the novel confinement properties of carbon nanotubes in a robust host.