Our conversation with Sir John Pendry, metamaterials pioneer and Frontiers in Optics keynote speaker.
Sir John Pendry's career has been filled with remarkable discoveries and achievements. From being knighted by the Queen of England in 2004 to sparking the imagination of the world by creating the first practical "invisibility cloak," Pendry's list of accomplishments is impressive and far-reaching.
As a condensed matter theorist, Pendry spent his career in academia, having been a professor at the London Imperial College for the past 30 years—most recently as the chair in theoretical solid state physics. His research interests spanned the areas of low-energy diffraction, electronic surface states, transportation in disordered systems and metamaterials. In 2005, Pendry was named a Fellow of the Optical Society for his distinguished contributions to the theory of photonic bandgap materials, left-handed metamaterials and negative refraction.
During his plenary session keynote at Frontiers in Optics/Laser Science, which will take place 16-20 October in San Jose, Calif., U.S.A., Pendry will discuss the recent progress that has been made toward the development of the theoretical "perfect lens," which has no limit of resolution.
When we last spoke to you in 2007, you noted that researchers were just beginning to explore negative refraction at optical frequencies. What progress has been made since then?
Thanks to the experimental realization of metamaterials, negative refraction as proposed long ago by Victor Veselago is now a well-established concept used in the design of radio frequency and terahertz systems. Theorists in particular have seized on these opportunities and proposed all sorts of new and surprising applications. Not all of them are practical, but some of them will find applications.
Researchers are currently addressing the difficulties of producing negative refraction at optical frequencies. Perhaps the most important development has been the connections between negative refraction and plasmonics. There has been much cross-fertilization, particularly in subwavelength devices.
How far have researchers come in invisibility cloaking since it was first demonstrated in 2006? What's next?
Scientists have made several demonstrations of the theory at radio frequencies, and now they are moving forward toward cloaking visible and near-visible light using the modified cloaking concept proposed by Jensen Li and myself—the so-called carpet cloak. The modest material demands of this new type of cloak have led to several realizations of optical cloaks with dimensions of several centimeters. The next step will be to work on translating these laboratory devices into practical applications.
Another interesting area of metamaterials research is the concept of a perfect lens. Are
you working in this area?
Currently at Imperial College, we have two thrusts in this direction. One is our "better than silver" project, which is a theoretical search for metals or alloys that are even better conductors than silver and that would therefore make better lenses. The other, related to the perfect lens, is toward the development of light-harvesting devices. We have theoretical designs that can gather light from the far-field and concentrate its energy into a volume only a few nanometers across, thus achieving enormous energy density. The next step will be to prove the concept experimentally. After that, we can move forward to finding applications in low-power nonlinear devices and lasing systems.
Early in your career you studied
electronic surface states and transport in disordered systems. What prompted your change in focus?
It was Eli Yablonovitch's acclaimed paper on photonic band gaps, which bridged the divide between optics and electronic structure. I realized that I had something to contribute to a new field.
Do you have a favorite research area?
I can't say that I do. Nearly every type of science interests me. My one regret is that I only have time to work in a few areas.
What would you say was your
I would say it was my realization of the potential to use structure in order to change the optical properties of a material, hence leading to the concept of a metamaterial. Alongside this, I am also proud of my development of transformation optics theory, which enables us to specify the material parameters required to produce a given flow of light.
What role do you hope to play in future developments in metamaterials?
The concept of metamaterials is established, and the tools of transformation optics are there to exploit them. I and others plan to build on them and move forward.
Can you give us a sneak preview
of your plenary keynote?
I shall be talking about sub-wavelength optics. At the sub-wavelength level, light breaks up into its component electric and magnetic fields, and the concept of a ray of light is meaningless. Fortunately, transformation optics is there to replace Snell's law of refraction. Snell told us how rays of light change with material parameters. Transformation optics works instead with the electric and magnetic field lines that are conceptually valid on sub-wavelength scales.
What's the best part of being
There is nothing more satisfying than to find a really difficult and meaty problem and then solve it. A lion hunting and eating its prey could not get more satisfaction!
Lyndsay Basista is OSA's public and government relations coordinator.