Showing papers by "Viktor A. Podolskiy published in 2016"

Spontaneous Emission in Nonlocal Materials

Abstract: 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. A record-high enhancement of a decay rate is observed, in agreement with the developed quantitative description of the Purcell effect in a nonlocal medium. An engineered material nonlocality introduces an additional degree of freedom into quantum electrodynamics, enabling new applications in quantum information processing, photo-chemistry, imaging, and sensing.

Epsilon-near-zero photonic wires

Abstract: We experimentally demonstrate epsilon-near-zero “photonic wires” supporting optical modes with effective wavelengths 10 times larger than the light's free space wavelength and improved propagation lengths Design, fabrication, and characterization of the wires will be discussed

Enhanced Optical Transmission through MacEtch‐Fabricated Buried Metal Gratings

Abstract: Metallic films with subwavelength apertures, integrated into a semiconductor by metal-assisted chemical etch (MacEtch), demonstrate enhanced transmission when compared to bare semiconductor surfaces. The resulting "buried" metallic structures are characterized spectroscopically and modeled using rigorous coupled wave analysis. These composite materials offer potential integration with optoelectronic devices, for simultaneous near-uniform electrical contact and strong optical coupling to free space.

Interscale mixing microscopy: far-field imaging beyond the diffraction limit

Abstract: Optical microscopy is widely used to analyze the properties of materials and structures, to identify and classify these structures, and to understand and control their responses to external stimuli. The extent of available applications is determined largely by the resolution offered by a particular microscopy technique. Here we present an analytic description and an experimental realization of interscale mixing microscopy, a diffraction-based imaging technique that is capable of detecting and characterizing wavelength/10 objects in far-field measurements with both coherent and incoherent broadband light. This technique is aimed at analyzing subwavelength objects based on far-field measurements of the interference created by the objects and a finite diffraction grating. A single measurement, analyzing the multiple diffraction orders, is often sufficient to determine the parameters of the object. The presented formalism opens opportunities for spectroscopy of nanoscale objects in the far field.

Homogenization of nanowire-based composites with anisotropic unit-cell and layered substructure

Abstract: We analyze the optical properties of composite materials that combine nanowire and nanolayer platforms. We revisit effective-medium theory (EMT) description of wire materials with high filling fraction positioned in anisotropic unit cells and present a simple numerical technique to extend Maxwell-Garnett formalism in this limit. We also demonstrate that the resulting EMT can be combined with transfer-matrix technique to adequately describe photonic band gap behavior, previously observed in epitaxially grown semiconductor multilayer nanowires.

Multiscale metasurfaces for enhanced light extraction

Abstract: Computationally designed multi-scale gratings demonstrating both diffractive and effective medium properties can dramatically increase optical coupling out of a high-index dielectric. Typical results show increase of transmission on the order of 20%.

Electrically Pumped Single Transverse-Mode Coupled Waveguide Lasers by Parity-time (PT) Symmetry

Abstract: We demonstrate single transverse-mode operation of broad-area coupled waveguide lasers enabled by parity-time (PT) symmetry. The PT symmetric laser operates on coupled waveguide cavities with electrically tuned gain and loss. Such counterintuitive waveguide design enables PT symmetric breaking, causing unique mode selection and ultimately enabling single mode operation. By electrically tuning the loss in the loss region of the coupled waveguide cavity, several different PT-symmetric regimes are analyzed theoretically, and the corresponding PT symmetric phase transition is demonstrated experimentally in the coupled waveguide laser.

Epsilon-Near-Zero Photonics Wires for Mid-Infrared Optical Lumped Circuitry

Abstract: 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. Our samples are characterized by polarization and angle-dependent FTIR spectroscopy and modeled by finite element methods and rigorous coupled wave analysis. We demonstrate coupling to such photonic wires from free space, and show the effective wavelength of the excited mode to be approximately an order of magnitude larger than the free-space wavelength of our light. The operational length of the photonic wires approaches twice the free space wavelength, significantly longer than what is achievable with bulk epsilon near zero materials. The novel architecture utilized in our hybrid waveguides allows for significant design flexibility by control of the semiconductor material's optical properties and the sample geometry. In addition, by utilizing a semiconductor-based architecture, our photonic wires can be designed to monolithically integrate the optical equivalents of capacitive, inductive, and resistive lumped circuit elements, as well optoelectronic sources and detectors. As such, the demonstrated photonic wires have the potential to provide a key component, and a realistic framework, for the development of optical circuitry.

Anisotropic and Hyperbolic Metamaterials

Abstract: For years, optics has been developed with the implicit assumption that underlying materials relatively weakly interact with optical radiation. Œus, optical media have been implicitly assumed to be nonmagnetic. Optical magnetism [1], experimentally realized [2-4] during the last decade, is fueling revolutionary growth in the area of metamaterials, nanostructured composites with tailored optical properties.

Spontaneous emission and non-radiative processes inside a hyperbolic metamaterial(Conference Presentation)

Abstract: Fluorescence-based processes are strongly modified by the electromagnetic environment in which the emitters are placed. Hence, the design of nanostructured materials with appropriate electromagnetic properties opens up a new route in the control of, for instance, the spontaneous rate of emission or the energy transfer rate in donor-acceptor pairs. In particular, hyperbolic plasmonic metamaterials have emerged as a very flexible and powerful platform for these applications as they provide a high local density of electromagnetic states due to their peculiar mode structure which is governed by both the structural nonlocal response and the dispersion properties. Here, we will discuss an experimental and theoretical study of the influence of a hyperbolic metamaterial comprised of an array of gold nanorods on the radiative properties of quantum emitters and the energy-transfer processes between them.

Homogenization of nanowire-based composites with anisotropic unit cell and layered substructure

Abstract: We present a simple numerical extension to Maxwell Garnett formalism for wire materials with high filling fractions in anisotropic unit cells to describe photonic band gap behavior observed in epitaxially grown semiconductor multilayer nanowires.

Interscale Mixing Microscopy: far field imaging beyond the diffraction limit

Abstract: 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. The presented formalism opens the door for spectroscopy of nanoscale objects in the far-field.

Buried extraordinary optical transmission

Abstract: Metallic films with subwavelength apertures integrated into a semiconductor exhibit broadband enhancement of light coupling into the semiconductor (compared to an unstructured surface) while providing near uniform electrical contact for potential integration into optoelectronic devices.