Research

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Our group is broadly interested in theoretical and computational research in plasmas, nanoelectronics, electromagnetic fields and waves, and accelerator technology. We identify the practical problems and explore the underlying physics for the development of novel nanoscale devices, emerging plasma and vacuum nanoelectronics, compact radiation sources (radio frequency – microwave – millimeter wave – THz – x-ray), and compact accelerators.

Here are examples of several particular research topics we are working on:

• Electron emission physics: Electron sources are important to applications such as microwave generation, space-vehicle neutralization, X-ray generation, e-beam lithography, and electron microscopy. We have been modeling the highly nonlinear electron emission from a metal surface illuminated by a laser. The very short electron bunches produced would enable many exciting technological developments, such as four-dimensional (4D) time-resolved electron microscopy.

• Electrical contacts & nanoscale charge transport: Contact resistance is the resistance to current flow, due to surface conditions and other causes (e.g. current flow constriction), when contacts (usually of dissimilar materials) are touching one another in a device. Contact resistance is one of the major limiting factors to devices made of exceptional materials, such as carbon nanotubes (CNTs), graphene, diamond, as well as emerging two-dimensional semiconductors such as atomically thin black phosphorus. We have been exploring the scalings of contact resistance and of nanoscale charge transport across interfaces, aiming to optimizing charge transport in various devices.

• Electron beam interaction with novel structures: When electrons propagate close to the surface of metallic periodic grating, electromagnetic radiation can be emitted by the so called Smith-Purcell (SP) effect. SP effect is one particularly promising choice for developing compact Near-infrared – THz – millimeter radiation sources, which have significant potential applications in high-resolution imaging, noninvasive sensing, high-data rate communications and material analysis. We have been developing various strategies to enhance coherent SP radiation, which is important to the development of high brightness compact light sources.

• Laser plasma interaction with QED effects: With continuous increase in the available laser intensity, studies of laser–plasma interactions are entering a new regime where the physics of relativistic plasmas is strongly affected by strong-field quantum electrodynamics (QED) processes, including hard photon emission and electron–positron pair production. This coupling of quantum emission processes and relativistic collective particle dynamics can result in dramatically new plasma physics phenomena, such as the generation of dense pair plasma from near vacuum, complete laser energy absorption by QED processes, or the stopping of an ultrarelativistic electron beam, which could penetrate a cm of lead, by a hair’s breadth of laser light. In addition to being of fundamental interest, it is crucial to study this new regime to understand the next generation of ultra-high intensity laser-matter experiments and their resulting applications, such as high energy ion, electron, positron, and photon sources for fundamental physics studies, medical radiotherapy, and next generation radiography for homeland security and industry.