Viktor A. Podolskiy

Viktor A. Podolskiy
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Viktor A. Podolskiy

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Physics - Optics (32)
Physics - General Physics (6)
Physics - Materials Science (5)
Physics - Disordered Systems and Neural Networks (1)
Nonlinear Sciences - Chaotic Dynamics (1)
Physics - Biological Physics (1)
Physics - Mesoscopic Systems and Quantum Hall Effect (1)

Publications Authored By Viktor A. Podolskiy

We consider the problem of light transmission from a high refractive index medium into a low index environment. While total internal reflection severely limits such transmission in systems with smooth interfaces, diffractive metasurfaces may help out-couple light that enters an interface at blazing angles. We demonstrate that the profile of the structured interface can be numerically optimized to target a particular emission pattern. Read More

We present a new formalism for understanding the optical properties of metasurfaces, optically thin composite diffractive devices. The proposed technique, Rigorous Diffraction Interface Theory (R-DIT), provides an analytical framework for understanding the transition between optically thin and optically thick structures. For metasurfaces, R-DIT avoids the calculation of optical propagation through thin layer and provides a direct link between the composition and geometry of a metasurface and its transmission, reflection, and diffraction properties. Read More

In this report, we demonstrate the single transverse-mode operation of InAs quantum dot (QD) broad-area coupled waveguide lasers by parity-time (PT) symmetry. A novel waveguide design is adopted by adding gain and loss in the electrically injected coupled waveguide laser cavity. In such counterintuitive waveguide design, the single mode operation is achieved by harnessing notions from PT symmetry breaking and mode selections. Read More

Light-matter interactions can be dramatically modified by the surrounding environment. Here we report on the first experimental observation of molecular spontaneous emission inside a highly nonlocal metamaterial based on a plasmonic nanorod assembly. We show that the emission process is dominated not only by the topology of its local effective medium dispersion, but also by the nonlocal response of the composite, so that metamaterials with different geometric parameters but the same local effective medium properties exhibit different Purcell factors. Read More

We present an analytical description and an experimental realization of interscale mixing microscopy, a diffraction-based imaging technique that is capable of detecting wavelength/10 objects in far-field measurements with both coherent and incoherent broadband light. This method aims at recovering the spatial spectrum of light diffracted by a subwavelength object based on far-field measurements of the interference created by the object and a finite diffraction grating. A single measurement, analyzing the multiple diffraction orders, is often sufficient to determine the parameters of the object. Read More

There has been recent interest in the development of optical analogues of lumped element circuitry, where optical elements act as effective optical inductors, capacitors, and resistors. Such optical circuitry requires the photonic equivalent of electrical wires, structures able carry optical frequency signals to and from the lumped circuit elements while simultaneously maintaining signal carrier wavelengths much larger than the size of the lumped elements. Here we demonstrate the design, fabrication, and characterization of hybrid metal/doped-semiconductor 'photonic wires' operating at optical frequencies with effective indices of propagation near-zero. Read More

The radiation dynamics of optical emitters can be manipulated by properly designed material structures providing high local density of photonic states, a phenomenon often referred to as the Purcell effect. Plasmonic nanorod metamaterials with hyperbolic dispersion of electromagnetic modes are believed to deliver a significant Purcell enhancement with both broadband and non-resonant nature. Here, we have investigated finite-size cavities formed by nanorod metamaterials and shown that the main mechanism of the Purcell effect in these hyperbolic resonators originates from the cavity hyperbolic modes, which in a microscopic description stem from the interacting cylindrical surface plasmon modes of the finite number of nanorods forming the cavity. Read More

We present a formalism for understanding the elecromagnetism of metasurfaces, optically thin composite films with engineered diffraction. The technique, diffractive interface theory (DIT), takes explicit advantage of the small optical thickness of a metasurface, eliminating the need for solving for light propagation inside the film and providing a direct link between the spatial profile of a metasurface and its diffractive properties. Predictions of DIT are compared with full-wave numerical solutions of Maxwell's equations, demonstrating DIT's validity and computational advantages for optically thin structures. Read More

We present an imaging technique that allows the recovery of the transparency profile of wavelength-scale objects with deep subwavelength resolution based on far-field intensity measurements. The approach, interscale mixing microscopy (IMM), relies on diffractive element positioned in the near-field proximity to the object, to scatter information carried by evanescent waves into propagating part of the spectrum. A combination of numerical solutions of Maxwell equations and nonlinear fitting is then used to recover the information about the object based on far-field intensity measurements. Read More

We present an analytical description of the nonlocal optical response of plasmonic nanowire metamaterials that enable negative refraction, subwavelength light manipulation, and emission lifetime engineering. We show that dispersion of optical waves propagating in nanowire media results from coupling of transverse and longitudinal electromagnetic modes supported by the composite and derive the nonlocal effective medium approximation for this dispersion. We derive the profiles of electric field across the unit cell, and use these expressions to solve the long-standing problem of additional boundary conditions in calculations of transmission and reflection of waves by nonlocal nanowire media. Read More

We demonstrate that homogeneous naturally-occurring materials can form non-magnetic negative refractive index systems, and present specific realizations of the proposed approach for the THz and far-IR frequencies. The proposed structure operates away from resonance, thereby promising the capacity for low-loss devices. Read More

We develop a quantitative description of giant asymmetry in reflectance, recently observed in semicontinuous metal films. The developed scaling-theory based technique reproduces the spectral properties of semicontinuous composites, as well as provides insight into the origin of experimentally observed loss, reflectance, and transmittance anomalies in the vicinity of the percolation threshold. Read More

Integration of the next generation of photonic structures with electronic and optical on-chip components requires the development of effective methods for confining and controlling light in subwavelength volumes. Several techniques enabling light coupling to sub-wavelength objects have recently been proposed, including grating-, and composite-based solutions. However, experi-mental realization of these couplers involves complex fabrication with \sim 10nm resolution in three dimensions. Read More

We analyze wave propagation in coupled planar waveguides, pointing specific attention to modal cross-talk and out-of-plane scattering in quasi-planar photonics. An algorithm capable of accurate numerical computation of wave coupling in arrays of planar structures is developed and illustrated on several examples of plasmonic and volumetric waveguides. An analytical approach to reduce or completely eliminate scattering and modal cross-talk in planar waveguides with anisotropic materials is also presented. Read More

We present a technique capable of producing subwavelength focal spots in the far-field of the source in planar non-resonant structures. The approach combines the diffraction gratings that generate the high-wavevector-number modes and planar slabs of homogeneous anisotropic metamaterials that propagate these waves and combine them at the subwavelength focal spots. In a sense, the technique combines the benefits of Fresnel lens, near-field zone plates, hyperlens, and superlens, and at the same time resolves their fundamental limitations. Read More

We develop an approach to utilize anisotropic metamaterials to solve one of the fundamental problems of modern plasmonics -- parasitic scattering of surface waves into free-space modes, opening the road to truly two-dimensional plasmonic optics. We illustrate the developed formalism on examples of plasmonic refractor and plasmonic crystal, and discuss limitations of the developed technique and its possible applications for sensing and imaging structures, high-performance mode couplers, optical cloaking structures, and dynamically reconfigurable electro-plasmonic circuits. Read More

We resolve the long standing controversy regarding the imaging by a planar lens made of left-handed media and demonstrate theoretically that its far field image has a fundamentally different origin depending on the relationship between losses {inside} the lens and the wavelength of the light $\lambda$. At small enough $\lambda$ the image is always governed by diffraction theory, and the resolution is independent of the absorption if both Im$\epsilon \ll 1$ and Im$\mu \ll 1$. For any finite $\lambda$, however, a critical absorption exists below which the superresolution regime takes place, though this absorption is extremely low and can hardly be achieved. Read More

We derive an approach to define the causal direction of the wavevector of modes in optical metamaterials, which in turn, determines signs of refractive index and impedance as a function of {\it real and imaginary} parts of dielectric permittivity and magnetic permeability. We use the developed technique to demonstrate that the interplay between resonant response of constituents of metamaterials can be used to achieve efficient dispersion management. Finally we demonstrate broadband dispersion-less index and impedance matching in active nanowire-based negative index materials. Read More

We show that a stack of metal-dielectric nanolayers, in addition to the long- and short-range plasmons, guides also an entire family of modes strongly confined within the multilayer - the bulk plasmon modes. We propose the classification scheme that reflects specific properties of these modes. We report experimental verification of the bulk plasmon modes by measuring modal indices in a structure made of three pairs of silica(29nm)/gold(25nm) layers. Read More

We report on design and fabrication of nano-composite metal-dielectric thin film coatings with high reflectance asymmetries. Applying basic dispersion engineering principles to model a broadband and large reflectance asymmetry, we obtain a model dielectric function for the metamaterial film, closely resembling the effective permittivity of disordered metal-dielectric nano-composites. Coatings realized using disordered nanocrystalline silver films deposited on glass substrates confirm the theoretical predictions, exhibiting symmetric transmittance, large reflectance asymmetries and a unique flat reflectance asymmetry. Read More

We analyze electromagnetic modes in multi-layered nano-composites and demonstrate that the response of a majority of realistic layered structures is strongly affected by the non-local effects originating from strong field oscillations across the system, and is not described by conventional effective-medium theories. We develop the analytical description of the relevant phenomena and confirm our results with numerical solutions of Maxwell equations. Finally, we use the developed formalism to demonstrate that multi-layered plasmonic nanostructures support high-index volume modes, confined to deep subwavelength areas, opening a wide class of applications in nanoscale light management. Read More

We study the energy propagation in subwavelength waveguides and demonstrate that the mechanism of material gain, previously suggested for loss compensation, is also a powerful tool to manipulate dispersion and propagation characteristics of electromagnetic pulses at the nanoscale. We show theoretically that the group velocity in lossy nano-waveguides can be controlled from slow to superluminal values by the material gain and waveguide geometry and develop an analytical description of the relevant physics. We utilize the developed formalism to show that gain-assisted dispersion management can be used to control the transition between ``photonic-funnel'' and ``photonic-compressor'' regimes in tapered nano-waveguides. Read More

We present a detailed study of light propagation in waveguides with anisotropic metamaterial cores. We demonstrate that in contrast to conventional optical fibers, our structures support free-space-like propagating modes even when the waveguide radius is much smaller than the wavelength. We develop analytical formalism to describe mode structure and propagation in strongly anisotropic systems and study the effects related to waveguide boundaries and material composition. Read More

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. Read More

We present waveguides with photonic crystal cores, supporting energy propagation in subwavelength regions with a mode structure similar to that in telecom fibers. We design meta-materials for near-, mid-, and far-IR frequencies, and demonstrate efficient energy transfer to and from regions smaller than 1/25-th of the wavelength. Both positive- and negative-refractive index light transmissions are shown. Read More

We analyze the performance of a planar lens based on realistic negative index material in a generalized geometry. We demonstrate that the conventional superlens design (where the lens is centered between the object and the image) is not optimal from the resolution point-of-view, develop an analytical expression for the resolution limit of a generalized lens, use it to find the optimum lens configuration, and calculate the maximum absorption practical nearfield superlenses may have. We demonstrate that in contrast to the conventional superlens picture, planar imaging is typically accompanied by excitation of surface waves at both interfaces of the lens. Read More

We develop an approach to use nanostructured plasmonic materials as a non-magnetic negative-refractive index system at optical and near-infrared frequencies. In contrast to conventional negative refraction materials, our design does not require periodicity and thus is highly tolerant to fabrication defects. Moreover, since the proposed materials are intrinsically non-magnetic, their performance is not limited to proximity of a resonance so that the resulting structure has relatively low loss. Read More

We demonstrate that non-magnetic ($\mu \equiv 1$) left-handed materials can be effectively used for waveguide imaging systems. We also propose a specific THz realization of the non-magnetic left-handed material based on homogeneous, naturally-occurring media. Read More

We compare the optical response of isolated nanowires, double-wire systems, and Pi-structures, and show that their radiation is well described in terms of their electric and magnetic dipole moments. We also show that both dielectric permittivity and magnetic permeability can be negative at optical and near infrared frequencies, and demonstrate the connection between the geometry of the system and its resonance characteristics. We conclude that plasmonic nanowires can be employed for developing novel negative-index materials. Read More

We develop a new approach to build a material with negative refraction index. In contrast to conventional designs which make use of a resonant behavior to achieve a non-zero magnetic response, our material is intrinsically non-magnetic and relies on an anisotropic dielectric constant to provide a left-handed response in waveguide geometry. We demonstrate that the proposed material can support surface (polariton) waves, and show the connection between polaritons and the enhancement of evanescent fields, also referred to as super-lensing. Read More

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

Classical counterparts of a great variety of quantum systems, from atomic physics to quantum wells and quantum dots, to optical, microwave, and acoustic resonators exhibit partially chaotic dynamics. Since it is often impossible to measure the temporal dynamics in qunatum systems, the main and probably the most dramatic manifestation of classical chaos in their phase space is seen in the distribution of spacing between the neighboring energy levels. While the mechanism leading to the onset of chaotic dynamics is different in every system, the level spacing distribution obeys the universal law, changing from Poissonian in the completely integrable systems to Wigner in completely chaotic ones. Read More