Our group concentrates on the optical and magneto-optical properties of materials grown by chemical synthesis, sputtering and molecular beam epitaxy.
Ongoing projects include development of silicon micro and nanowires for non-linear and terahertz optics, and deposition of II-VI materials for waveguide laser applications. Characterization of optical, electrical and magnetic properties often includes use of NanoLab facilities.
Optical materials and nanostructures
Current topics of interest include novel photonic materials and growth methods, transport in nanostructures and resonant optical structures. We are pursuing the development of transition metal doped II-VI compounds for mid-IR lasers and semiconductor-core optical fibers.
One method to produce large quantities of micro and nanostructured materials is to draw them into the core of a glass fiber. This allows heat treatments to control the crystal structure and local composition of the core contents. In-fiber fabrication of p-n junctions for solar energy and for electrical control of optical signals is a long-term goal of this project. Collaborative studies of material transport in these materials is underway.
Molecular beam epitaxy and optical properties of ZnS
Ultra-high vacuum growth of transition metal-doped ZnS is being investigated for potential applications as a laser material and a candidate for Intermediate Band Solar Cells. Clustering of the impurities is deleterious when there is only one impurity, but combining two dopants is expected to lead to improved performance. In collaboration with Irina Sorokina.
Optical properties of nanostructures and nanoparticles
The optical properties of periodic structures with dimensions on the order of the wavelength produce interesting phenomena, such as interference-based optical filters. We are investigating the properties of materials where the subwavelength structure is purposefully manipulated to modify the optical response of a system. This includes 0-, 1- and 2-dimensional periodic structures with length scales of 10nm-100nm. Both active and passive structures are being investigated.
Structure and composition information for SiGe microwires
The top images are for material with 25% Ge, which crystallize in a highly non-equilibrium condition and form dendrites. The lower images are for 6% Ge and illustrate some compositional non-uniformity that can be removed by laser recrystallization.