Ultrafast Optical Modulation by Virtual Interband Transitions

A new frontier in optics research has been opened by the recent developments in non-perturbative optical modulation in both time and space that creates temporal boundaries generating ``time-reflection'' and ``time-refraction'' of light in the medium. The resulting formation of a Photonic Time Crystal within the modulated optical material leads to a broad range new phenomena with a potential for practical applications, from non-resonant light amplification and tunable lasing, to the new regime of quantum light-matter interactions. However, the formation of the temporal boundary for light relies on optical modulation of the refractive index that is both strong and fast even on the time scale of a single optical cycle. Both of these two problems are extremely challenging even when addressed independently, leading to conflicting requirements for all existing methods of optical modulation. However, as we show in the present work, an alternative approach based on virtual interband transition excitation, solves this seemingly insurmountable problem. Being fundamentally dissipation-free, optical modulation by virtual excitation does not face the problem of heat accumulation and dissipation in the material, while the transient nature of the excited virtual population that modifies the material response only on the time scale of a single optical cycle, ensures that the resulting change in the refractive index is inherently ultrafast. Here we develop the theoretical description of the proposed modulation approach, and demonstrate that it can be readily implemented using already existing optical materials and technology.Comment: 6 pages, 4 figure

Beyond Stefan-Boltzmann Law: Thermal Hyper-Conductivity

We demonstrate that the broadband divergence of the photonic density of states in hyperbolic metamaterials leads to giant increase in radiative heat transfer, beyond the limit set by the Stefan-Boltzmann law. The resulting radiative thermal "hyper-conductivity" may approach or even exceed heat conductivity via electrons and phonons in regular solids

Control of absorption with hyperbolic metamaterials

We show that absorption of thin dye-doped polymeric films can be tuned and enhanced ( nearly threefold) by metallic and lamellar metal-dielectric hyperbolic metamaterial substrates. The effect can be controlled by a combination of the substrate\u27s geometry and composition. As the enhancement of absorption is sustained over large range of incidence angles, the demonstrated phenomenon can lead to a variety of important applications, including solar cell technology. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4703931

Nanowire metamaterials with extreme optical anisotropy

We study perspectives of nanowire metamaterials for negative-refraction waveguides, high-performance polarizers, and polarization-sensitive biosensors. We demonstrate that the behavior of these composites is strongly influenced by the concentration, distribution, and geometry of the nanowires, derive an analytical description of electromagnetism in anisotropic nanowire-based metamaterials, and explore the limitations of our approach via three-dimensional numerical simulations. Finally, we illustrate the developed approach on the examples of nanowire-based high energy-density waveguides and non-magnetic negative index imaging systems with far-field resolution of one-sixth of vacuum wavelength.Comment: Updated version; accepted to Appl.Phys.Let