3rd Intl. Conference on Metamaterials, Photonic Crystals and Plasmonics
META 12, the 3rd International Conference of Metamaterials, Photonic Crystals and Plasmonics, was held 19-22 April in Paris, France. The conference was widely attended, with morning plenary sessions followed by smaller focused sessions. Reflecting how diverse the fields have become and how many attendees participated, up to seven parallel sessions were held, covering numerous sub-topics of the conference themes. The organizers, Said Zouhdi (Paris-Sud University, France) and Xavier Begaud (Telecom ParisTech, France), did a spectacular job in coordinating the roughly 80 sessions and more than five hundred paper contributions.
Tremendous plenary talks were presented by Eli Yablonovitch (U. C. Berkeley), who discussed the relationship between the two possible descriptions of metals at optical wavelengths, pointing out the antenna concept remains underexploited in optics; Nader Engheta, who discussed the path towards full metamaterial systems; Naomi Halas, who described a variety of potential metamaterial and plasmonic applications, including the use of Fano or “dark” modes to bring advanced functionality into nanocomposites; and Harald Giessen, who continues to press the envelope in three-dimensional metamaterial fabrication. Vladimir Shalaev discussed gain in metamaterials as well as the recently reported “generalized refraction” experiments, and Sir John Pendry described how electron-electron interactions may ultimately be the limiting factor in plasmonic phenomena.
It is impossible to sum up or even begin to describe what we take away from the rich content of a conference such as META 12! We randomly choose just a few topics that resonate with some of the ongoing interests of our Center.
It was particularly interesting to hear the discussions surrounding the phenomena associated with sub-nanometer gaps and regions of metallic nanoparticles. We compare, for example, two talks: Javier Aizpurua, “Close encounters between nanoantennas: bridging quantum and classical plasmonics” (in Quantum Metamaterials I); and Sir John Pendry, “Inside the wavelength: seeing really small objects with light” (in Plenary Session III). There is agreement on all sides that to obtain maximum field enhancements, the separation between plasmonic nanoparticles must be as small as possible. We are rapidly reaching the point that we can controllably position nanoparticles with separation distances of less than a nanometer. At this scale, however, the classical view of the metal as a homogeneous medium with a discrete interface is not appropriate. At META'12, the invited talks of Aizpurua and Pendry addressed such plasmonic systems using two different approaches.
Aizpurua presented a fully quantum mechanical investigation of two metal nanospheres separated by vacuum. A numerical simulation of the three dimensional plasmonic system was realized. Aizpurua suggested the crucial role of tunnel conduction between the two particles of the dimer.
Pendry presented an analytical approach based on the non-local response of the metal arising from quantum pressure, applying transformation optics to treat the simplified system of two nanocylinders. Using a conformal transformation, the two cylinders are transformed into two metal semi-infinite media separated by vacuum. Then, a nonlocal hydrodynamical Drude model is used for the permittivity of the metal and the response of the system is determined using a modal expansion.
It is interesting to note that, while the two approaches are quite different, they arrive at nearly identical results. Some of the content of the two invited talks is discussed in two recent articles, which we mention in the “what we’re reading” section of the newsletter.
One of the fascinating possibilities for metamaterials is as use as “perfect absorbers.” While many in the metamaterials community try to avoid the normally large absorption and damping in metamaterials, some embrace it, building surfaces that absorb light with great efficiency. Given the equivalence between absorptivity and emissivity in equilibrium, perfect absorbing structures can be designed for a range of interesting applications, as discussed in Willie Padilla’s talk “Metamaterials for tailored thermal infrared emission,” (in Photothermal effects in plasmonics and metamaterials II). And, yes, losses are the hero here, not the villain!
The use of metamaterials for diffractive optics has quickly become a research theme, with numerous talks describing how structured metamaterials and plasmonic media can provide new opportunities for steering and manipulating light. B. Walther presented “Multi-wavelength holograms from plasmonic metamaterials,” (in Metamaterials for Diffractive Components II), in which holograms were formed at two wavelengths in the visible spectrum using a fishnet-type metamaterial. At the Center, we’re also very excited to be studying diffractive metamaterial optics, which have the advantage of only requiring a thin amount of material to perform complex operations on light. The use of the fishnet metamaterial for diffractive optics is described in a recent paper by Walther and colleagues, referenced in the “what we’re reading” section of the newsletter.
These are just a few of the many, many interesting talks and posters presented at META 12. To get more details, the entire program is available click here.
David Smith presenting at META 12.
David R. Smith, Director of CMIP gave three talks at META 12, including "Leveraging Enhanecement of Metamaterials of Nonlinear and Quantum Optical Applications"
Abstract: Metamaterials have become widely appreciated for their ability to enable new or difficult material properties, including complex distributions of constitutive parameters. The result is that we have at our disposal an expanded set of tools for controlling the propagation of light. Still, mimicking the intrinsic response of materials is just one function that metamaterials can provide; enhancing nonlinearity and photodynamic processes is another feature that is yet in the early stages of being exploited. By gaining control over the field enhancement associated with metal nanostructures, new classes of quantum metamaterials are possible that not only control wave propagation but also couple strongly to fundamental radiative processes.
Stéphane Larouche, Research Scientist in CMIP presented, "Mixed nonlinearity retrieval and spatial dispersion in nonlinear metamaterials."
Abstract: A method to retrieve both effective electric and magnetic nonlinear susceptibilities of metamaterials is presented. This method is applied to simplified unit cells with only electric nonlinearity to isolate the effect of spatial dispersion, which shows as a magnetic nonlinearity. A criteria for homogenization of nonlinear metamaterials is proposed.
Steven Cummer, Faculty in ECE at Duke presented, "Implementation of Metamaterials for Transformation Acoustics Applications."
Abstract: We review the detailed development and derivation of the concept of transformation acoustics and demonstrate several approaches for engineering materials with the acoustic properties needed to realize transformation acoustics devices.