Extending plasmonic response to the mid-wave infrared with all-epitaxial composites.

Highly doped semiconductor "designer metals" have been shown to serve as high-quality plasmonic materials across much of the long-wavelength portion of the mid-infrared. These plasmonic materials benefit from a technologically mature semiconductor fabrication infrastructure and the potential for monolithic integration with electronic and photonic devices. However, accessing the short-wavelength side of the mid-infrared is a challenge for these designer metals.

Ghost-induced exact degeneracies.

We show that ghost waves-a special class of nonuniform waves in biaxial dielectric media-can lead to exact frequency degeneracies in guided modes. These degeneracies offer a new way of controlling mode interactions with a broad range of potential applications, from integrated waveguides to nonlinear optics and optical sensing.

Incoherent perfect absorption in lossy anisotropic materials.

We show that perfect absorption of incoherent light is possible in a semi-infinite slab of anisotropic dielectric even in the presence of loss. The operating frequency of the proposed system is free of any dependence on physical dimensions.

Experimental Demonstration of Hyperbolic Metamaterial Assisted Illumination Nanoscopy.

An optical metamaterial is capable of manipulating light in nanometer scale that goes beyond what is possible with conventional materials. Taking advantage of this special property, metamaterial-assisted illumination nanoscopy (MAIN) possesses tremendous potential to extend the resolution far beyond conventional structured illumination microscopy. Among the available MAIN designs, hyperstructured illumination that utilizes strong dispersion of a hyperbolic metamaterial (HMM) is one of the most promising and practical approaches, but it is only theoretically studied.

Thermal radiation of Er doped dielectric crystals: Probing the range of applicability of the Kirchhoff's law.

Kirchhoff's law of thermal radiation, relating emissivity and absorptance is commonly formulated for opaque bodies in thermodynamic equilibrium with the environment. However, in many systems of practical importance, both assumptions are often not satisfied. We revisit the century-old law and examine the limits of its applicability in an example of Er:YAG and Er:YLF dielectric crystals-potential radiation converters for thermophotovoltaic applications.

Photonic hypercrystals for control of light-matter interactions.

Photonic crystals (PCs) have emerged as one of the most widely used platforms for controlling light-matter interaction in solid-state systems. They rely on Bragg scattering from wavelength-sized periodic modulation in the dielectric environment for manipulating the electromagnetic field. A complementary approach to manipulate light-matter interaction is offered by artificial media known as metamaterials that rely on the average response of deep-subwavelength unit cells.

Optical phase retrieval using conical refraction in structured media.

We propose a method of optical phase retrieval based on the conical refraction imaging in structured media. We show that a multilayered dielectric photonic crystal functioning as a conically refractive flat lens can be used to reconstruct phase information of complex optical signals. Our method enables a single simultaneous measurement of multiple images on the same image plane and allows a rapid stable recovery of the optical phase.

Broadband Enhancement of Spontaneous Emission in Two-Dimensional Semiconductors Using Photonic Hypercrystals.

The low quantum yield observed in two-dimensional semiconductors of transition metal dichalcogenides (TMDs) has motivated the quest for approaches that can enhance the light emission from these systems. Here, we demonstrate broadband enhancement of spontaneous emission and increase in Raman signature from archetype two-dimensional semiconductors: molybdenum disulfide (MoS2) and tungsten disulfide (WS2) by placing the monolayers in the near field of a photonic hypercrystal having hyperbolic dispersion. Hypercrystals are characterized by a large broadband photonic density of states due to hyperbolic dispersion while having enhanced light in/out coupling by a subwavelength photonic crystal lattice.

Long-range wetting transparency on top of layered metal-dielectric substrates.

It has been recently shown that scores of physical and chemical phenomena (including spontaneous emission, scattering and Förster energy transfer) can be controlled by nonlocal dielectric environments provided by metamaterials with hyperbolic dispersion and simpler metal/dielectric structures. At this time, we have researched van der Waals interactions and experimentally studied wetting of several metallic, dielectric and composite multilayered substrates. We have found that the wetting angle of water on top of MgF2 is highly sensitive to the thickness of the MgF2 layer and the nature of the underlying substrate that could be positioned as far as ~100 nm beneath the water/MgF2 interface.

Realization of mid-infrared graphene hyperbolic metamaterials.

While metal is the most common conducting constituent element in the fabrication of metamaterials, graphene provides another useful building block, that is, a truly two-dimensional conducting sheet whose conductivity can be controlled by doping. Here we report the experimental realization of a multilayer structure of alternating graphene and Al2O3 layers, a structure similar to the metal-dielectric multilayers commonly used in creating visible wavelength hyperbolic metamaterials. Chemical vapour deposited graphene rather than exfoliated or epitaxial graphene is used, because layer transfer methods are easily applied in fabrication.

Dirac dispersion in photonic hypercrystals.

Photonic hypercrystals--the recently introduced concept of artificial optical media that combines the properties of hyperbolic metamaterials and photonic crystals [E. Narimanov, Phys. Rev.

Frequency comb formation and transition to chaos in microresonators with near-zero dispersion.

We investigate the frequency comb formation in microresonators with near-zero dispersion, study the route from integrability to chaos in the corresponding nonlinear system, and demonstrate the key role of nonlinear dynamics of such a system for frequency comb generation and stability.

Self-assembled tunable photonic hyper-crystals.

We demonstrate a novel artificial optical material, the "photonic hyper-crystal", which combines the most interesting features of hyperbolic metamaterials and photonic crystals. Similar to hyperbolic metamaterials, photonic hyper-crystals exhibit broadband divergence in their photonic density of states due to the lack of usual diffraction limit on the photon wave vector. On the other hand, similar to photonic crystals, hyperbolic dispersion law of extraordinary photons is modulated by forbidden gaps near the boundaries of photonic Brillouin zones.

Zeroth-order transmission resonance in hyperbolic metamaterials.

We present a new approach to subwavelength optical confinement, based on hyperbolic media in planar Fabry-Perot geometry. Unlike higher-order resonance modes in indefinite metamaterial cavities, the predicted resonance corresponds to 0th-order mode and can be observed in planar systems. Our approach combines subwavelength light confinement with strong radiative coupling, enabling a practical planar design of nanolasers and subwavelength waveguides.

Metric signature transitions in optical metamaterials.

We demonstrate that the extraordinary waves in indefinite metamaterials experience an (--++) effective metric signature. During a metric signature change transition in such a metamaterial, a Minkowski space-time is created together with a large number of particles populating the space-time. Such metamaterial models provide a tabletop realization of metric signature change events suggested to occur in Bose-Einstein condensates and quantum gravity theories.

Cylinder light concentrator and absorber: theoretical description.

We present a detailed theoretical description of a broadband omnidirectional light concentrator and absorber with cylinder geometry. The proposed optical "trap" captures nearly all the incident light within its geometric cross-section, leading to a broad range of possible applications--from solar energy harvesting to thermal light emitters and optoelectronic components. We have demonstrated that an approximate lamellar black-hole with a moderate number of homogeneous layers, while giving the desired ray-optical performance, can provide absorption efficiencies comparable to those of ideal devices with a smooth gradient in index.

Chaos-assisted directional light emission from microcavity lasers.

We study the effect of dynamical tunneling on emission from ray-chaotic microcavities by introducing a suitably designed deformed disk cavity. We focus on its high quality factor modes strongly localized along a stable periodic ray orbit confined by total internal reflection. It is shown that dominant emission originates from the tunneling from the periodic ray orbit to chaotic ones; the latter eventually escape from the cavity refractively, resulting in directional emission that is unexpected from the geometry of the periodic orbit, but fully explained by unstable manifolds of chaotic ray dynamics.

Semiclassical description of non magnetic cloaking.

We present a semiclassical description of non-magnetic cloaking. The semiclassical result is confirmed by numerical simulations of a gaussian beam scattering from the cloak. Further analysis reveals that certain beams penetrate the non-magnetic cloak thereby degrading the performance.

Impedance-matched hyperlens.

We propose an approach to optical imaging beyond the diffraction limit, based on transformation optics in concentric circular cylinder domains. The resulting systems allow image magnification and minimize reflection losses due to the impedance matching at the input or output boundaries. While perfect impedance matching at both surfaces can be obtained only in a system with radius-dependent magnetic permeability, we demonstrate that comparable performance can be achieved in an optimized nonmagnetic design.

Negative refraction in semiconductor metamaterials.

An optical metamaterial is a composite in which subwavelength features, rather than the constituent materials, control the macroscopic electromagnetic properties of the material. Recently, properly designed metamaterials have garnered much interest because of their unusual interaction with electromagnetic waves. Whereas nature seems to have limits on the type of materials that exist, newly invented metamaterials are not bound by such constraints.

Analysis of stealth communications over a public fiber-optical network.

We evaluate the security performance of the recently proposed "stealth" approach to covert communications over a public fiber-optical network. We present quantitative security analysis to assess the vulnerability of such systems against different attacks executed by an eavesdropper. We demonstrate the security advantage of the system by examining the BER/SNR performance as a function of the fidelity of the decoder used by an eavesdropper.

A method for secure communications over a public fiber-optical network.

We develop a spread-spectrum based approach to secure communications over existing fiber-optical networks. Secure transmission for a dedicated user is achieved by overlaying a covert channel onto a host channel in the existing active fiber link. The covert channel is optically encoded and temporally spread, and has average power below the noise floor in the fiber, making it hidden for a direct detection thus allowing for cryptographic and steganographic security capabilities.

Chaos-assisted tunneling in dielectric microcavities.

We demonstrate that the lifetimes and emission patterns of the optical modes in generic (asymmetric) microresonators are strongly affected by the phenomenon of chaos-assisted tunneling and develop a theory of the effect.

Near-sighted superlens.

We consider the problem of subwavelength imaging via a slab of a left-handed medium (LHM) in the presence of material losses. We derive the analytical expression for the resolution limit of a LHM-based lens and demonstrate that the area of its subwavelength performance is usually limited to the near-field zone.