Gradient Index Materials
Gradient-index (GRIN) materials have an index of refraction that varies as a function of position. Research in our group focuses on glass and plastic GRIN lenses to be used in optical systems. These elements are useful to a lens designer since they provide additional degrees of freedom, and thus can improve system performance. Research topics currently pursued range from the beginning of the process (fabricating the GRIN materials) to end applications (designing and tolerancing the optical systems).
Liquid Crystals Under Two Extremes: High-Power Laser Irradiation and Single-Photon Level
Both high-power laser applications and using liquid crystals as the host in a single-emitter confocal fluorescence microscopy require highly purified liquid crystal materials including oxygen depletion in some experiments. Collaboration with the Laboratory for Laser Energetics (LLE) with its liquid crystal clean room facility permitted preparation of liquid crystal cells for both applications. Purified at LLE monomeric cholesteric liquid crystal mixtures permitted to exclude thermal effects of impurities in obtaining athermal helical pitch dilation and unwinding in the field of the light wave. Planar alignment of cholesteric and nematic liquid crystals doped with single emitters for single-photon sources with definite linear and circular polarizations and for other quantum optical experiments was made using the LLE facility. With highly precise photoalignment and tunability of refractive index with applied electric field we are planning to continue to use liquid crystals for single-photon applications. Another direction of our research is cholesteric laser.
Professor Boyd is interested in the development of nonlinear optical materials, especially nanocomposite materials with enhanced response as a consequence of local field effects.
Nanoscale Semiconductor Materials
The Krauss group studies the fundamental optical properties of materials with a size in between individual molecules and macroscopic objects. These nanometer scale materials have physical characteristics that are strong functions of their size and shape, with properties that can be easily manipulated to address a given application. Currently the group is interested in the interaction of light with carbon nanotubes and semiconductor nanocrystal quantum dots. A variety of experimental approaches are used including single molecule microscopy and spectroscopy and ultrafast optical spectroscopy, either alone or combined with atomic force microscopy. These experiments probe at a fundamental level the nature of the optically excited state in these materials and excited state dynamics. Of particular interest are materials that are optically active in the near infrared at wavelengths relevant to optical communications or biological imaging. Applications for these materials are also being pursued in areas of nonlinear optics, renewable energy, and optoelectronics.
Semiconductor Epitaxial Structures
Molecular beam epitaxy is used to construct crystal structures, e.g. quantum wells and quantum dots. These types of structures are engineered for specific optical properties such as particular emission wavelengths or enhanced absorptions efficiencies.