We are interested in the physics and development of novel electronic and magnetic devices, as well as exploring fundamental optical interactions between light and matter. Our research areas cover a wide range with an emphasis on novel semiconductors, magnetic heterostructures, colossal magnetoresistance materials, and high-TC superconductors. The focus of our research is on understanding dynamical processes (electronic, magnetic, and vibrational) localized at surfaces and interfaces, and in the bulk at defects and impurities. Most of our research involves nonlinear optical techniques based on ultrafast high-power lasers which provide femtosecond time resolution and allow characterization of buried interfaces which are not easily accessible by conventional surface probes.

If you are planning on pursuing a Ph.D. degree at the interface between Physics and Electrical Engineering, please contact me (luepke@jlab.org) for more information and include your resume.

=====================================================================================================================================

Vibrational Dynamics of Defects in Semiconductors

The goal of this project is to elucidate the dynamics of the localized vibrational modes (LVMs) of defects related to light impurity in crystalline semiconductor, including Si, Ge and GaAs. >>Erik Spahr || Pjerin Luli

=====================================================================================================================================

Magnetic Heterostructure

The use of carrier spin as a new degree-of-freedom in semiconductor devices offers new functionality and enhanced performance. Efficient electrical injection of spin-polarized carriers into semiconductor heterostructures is an essential requirement to implement semiconductor spintronic devices. Significant progress has been made using magnetic semiconductor and ferromagnetic metals as spin injection contacts. >> Haibin Zhao || Yichun Fan

=====================================================================================================================================

Colossal Magnetoresistive Perovskite Manganese Oxides

Magnetoresistance(MR), i.e., the resistance change induced by an external magnetic field,is a phenomenon observed, more or less, in all metals and semiconductors. The recent interest in MR in doped manganites was initiated by the discovery of a large room temperature MR in epitaxial thin films. The doped manganites with large MR effect open up new possibilities for applications in diverse areas of technology such as magnetic random access memories and read heads for hard disk drives. >> Haibin zhao || Kevin Smith

=====================================================================================================================================

Magneto-Optical Imaging of Superconductors

The goal of this project is to study the relation between vortex dynamics and AC losses in High Temperature Superconductors cables under normal device operation. To achive this objective we developed a new Time-Resolved Magneto-Optical Imaging (TR-MOI) technique.

>> Andrea Lucarelli || Ran Yang

=====================================================================================================================================

Ultra-Short Laser Pulse Beam Shaping

We studied the spatial average intensity profile of an ultrashort laser pulse passing through a laser beam shaping system, which uses diffractive optical elements to reshape the Gaussian beam profile into a flat-top distribution. The Nonlinear Schrodinger Equation is solved numerically to simulate the nonlinear optical effects in this system. Our data and calculation show that this system works well for ultrashort pulses (> 100 fs). We also studied the effects of lateral misalignment, beam size deviation and defocusing on the beam intensity profile. >> Shuyan Zhang