Our research group engages in a wide variety of research in the fields of optics and photonics, device physics, and nanoscale science and technology. The following topics and descriptions are representative of our past and ongoing research, though new research directions are always emerging.
Thin film optics
Thin film interference is a well-understood and well-studied optical phenomenon responsible for the wide spectrum of colors that emerge from oil films on water, in soap bubbles, and in peacock feathers. The topic has a long history in the context of optical technology where interference coatings are used to improve the performance of microscope objectives, filters, and various other optical components. Though the field is quite mature, we have been able to discover new optical phenomena that have previously escaped notice. For example we have observed interference colors from films made up of 10-20 atomic layers, much thinner than ever seen before. This effect allows atomic layers to be visible with the naked eye and will have applications in ultra-thin optoelectronic devices such as photodetectors and solar cells. For an introduction of our work on thin film optics check out our recent article in Optics and Photonics News.
Optical metasurfacesConventional optical components including lenses, prisms, and waveplates rely on gradual accumulation of optical phase over length scales that are larger than the wavelength of light. This places a lower bound on the size and weight of such optical components. We developed a new class of optical components dubbed 'metasurfaces' which can be used to manipulate the phase, amplitude, and polarization of light in nearly arbitrary ways, and are hundreds of times thinner and lighter than conventional optics. Our metasurfaces are ultra-thin (tens of nanometers thick), perfectly flat, and provide control over the optical far-field and meso-field. These metasurfaces can be made for spectral ranges from the visible to the infrared and terahertz, and may prove to be especially useful outside of the visible range where there conventional optical technology is less developed. To learn more about metasurfaces take a look at our review article in IEEE or a review article from our colleagues in Nature Materials.
PlasmonicsTraditionally metals have had a limited role in optics, being primarily used as reflecting surfaces. However with the advent of nanofabrication technologies the field of plasmonics has emerged, which concerns the interaction of light with nanostructured metals. Plasmonic nanostructures are now widely used for enhancing intrinsically inefficient optical phenomena such as certain nonlinear processes and even linear absorption in tiny volumes. We have used plasmonics to create phased antenna metasurfaces (described above), to guide terahertz radiation, and to shape optical beams from semiconductor lasers. Because plasmonics is still a relatively new field, we also take the time to investigate fundamental issues such as the effect of radiation reaction and spectral broadening in plasmonic nanostructures.
Thermal radiation (or "blackbody" radiation) is a ubiquitous process responsible for light emission from incandescent light bulbs, hot stove-tops, and even the sun. Every object or material is constantly emitting some amount of thermal radiation in various frequency ranges; for example humans emit primarily in the infrared, which is one of the reasons why infrared cameras are often used for night-time imaging. The modern theory that describes blackbody radiation was one of the first major successes of quantum mechanics. A major goal of our research is to design the emission of thermal radiation. Suitably engineered thermal emitters will find uses in temperature regulation, thermal camouflage, and solar energy applications. As one dramatic example of thermal emission engineering, we recently created an object that actually appears cooler on an infrared camera as it is heated.