Our research focuses on the science and technology of nonlinear optical materials.  The work straddles materials science, physics, and optical engineering. We have three areas of current interest:

1. Multiferroics: Multiferroics are an exciting class of materials that have co-existing ferroelectricity and magnetism.   To study the coupled dynamics of electrical and magnetic domains, we are performing real-time nonlinear optical probing with simultaneous measurement of coupled properties such as magnetoelectric effect, electro-optic and magneto-optic effects, hysteresis, and dielectric spectroscopy.  The nanoscale structure of single domain walls is studied using scanning probe techniques such as piezoelectric force-, magnetic force-, nonlinear dielectric-, electric force- , and near-field scanning optical microscopies. Modeling tools include Ginzburg-Landau phenomenology, finite element method, and electromagnetic simulations.
2. Nonlinear optical devices:  We are developing a new class of devices by integrating diverse optical functionalities, such as optical frequency conversion, beam steering, dynamic focusing, beam shaping and high-speed switching, on a single ferroelectric chip by microengineering ferroelectric domains into gratings, lenses, prisms, and other arbitrary shapes.
3. Hybrid semiconductor-metal-oxide nanostructures:  In a recent breakthrough with Badding group (Chemistry), we have demonstrated microstructured silica optical fibers which contain hundreds of extreme aspect ratio (~105) semiconductor and metal-filled nanowires in a highly periodic array.  We are currently characterizing light guiding and nonlinear optical responses of these hybrid fibers. 

 Experimental tools include ultrafast femtosecond lasers, electro-optics and fiber optics, scanning probe microscopies, dielectric and magnetic measurements, clean room, cryogenics, and simulations based on home-written MATLAB as well as commercial codes.

Dr. Redwing’s research interests lie in the general area of electronic and optoelectronic materials synthesis and characterization with a special emphasis on chemical vapor deposition processing of semiconductor thin films and nanostructures. A current area of research focuses on the growth of semiconductor nanowires utilizing a combination of templating and directed growth techniques. This work is aimed at understanding the fundamental mechanisms of nanowire growth and the impact of nanoscale phenomena on materials synthesis. The fabrication of radial and axial nanowire heterostructures and p-n junctions is also under investigation for nanoscale device development. This research is an integral part of several multidisciplinary research team projects at Penn State which are focused on the development of nanowire-based devices for applications in microelectronics, chemical and biological sensing and solar energy conversion. The deposition of wide bandgap group III-nitride ((Al,Ga,In)N) thin films by metalorganic chemical vapor deposition is another active area of research. These materials are used in a wide variety of electronic and optoelectronic devices including high brightness light emitting diodes used in solid state lighting and high frequency/high power transistors for radar and wireless networks. The development of group III-nitride devices is often limited by film cracking which results from intrinsic and extrinsic stress due to lattice and thermal expansion mismatches between the film and substrate. The research is focused on understanding the microstructural mechanisms responsible for film stress and developing strategies to mitigate stress and film cracking. In-situ laser reflectance is used to study dynamic changes in film stress during deposition. This information is correlated to changes in film microstructure and dislocation density measured post-growth and is used to develop models of stress generation and relaxation in the group III-nitride materials system.