Person: Russell, Kasey
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Russell
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Kasey
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Russell, Kasey
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Publication Low threshold, room-temperature microdisk lasers in the blue spectral range(American Institute of Physics (AIP), 2013) Aharonovich, Igor; Woolf, Alexander J; Russell, Kasey; Zhu, Tongtong; Niu, Nan; Kappers, Menno J.; Oliver, Rachel; Hu, EvelynInGaN-based active layers within microcavity resonators offer the potential of low threshold lasers in the blue spectral range. Here, we demonstrate optically pumped, room temperature lasing in high quality factor GaN microdisk cavities, containing InGaN quantum dots (QDs) with thresholds as low as \(0.28 mJ/cm^2\). The demonstration of lasing action from GaN microdisk cavities with QDs in the active layer, provides a critical step for the nitrides in realizing low threshold photonic devices with efficient coupling between QDs and an optical cavity.Publication Controlled mode tuning in 1-D ‘RIM’ plasmonic crystal trench cavities probed with coupled optical emitters(Optical Society of America, 2013) Liu, Tsung-li; Russell, Kasey; Cui, Shanying; Hu, EvelynWe present a design of plasmonic cavities that consists of two sets of 1-D plasmonic crystal reflectors on a plasmonic trench waveguide. A 'reverse image mold' (RIM) technique was developed to pattern high-resolution silver trenches and to embed emitters at the cavity field maximum, and FDTD simulations were performed to analyze the frequency response of the fabricated devices. Distinct cavity modes were observed from the photoluminescence spectra of the organic dye embedded within these cavities. The cavity geometry facilitates tuning of the modes through a change in cavity dimensions. Both the design and the fabrication technique presented could be extended to making trench waveguide-based plasmonic devices and circuits.Publication Transistors Formed from a Single Lithography Step Using Information Encoded in Topography(Wiley-Blackwell, 2010) Dickey, Michael D.; Russell, Kasey; Lipomi, Darren J.; Narayanamurti, Venkatesh; Whitesides, GeorgeThis paper describes a strategy for the fabrication of functional electronic components (transistors, capacitors, resistors, conductors, and logic gates but not, at present, inductors) that combines a single layer of lithography with angle-dependent physical vapor deposition; this approach is named topographically encoded microlithography (abbreviated as TEMIL). This strategy extends the simple concept of ‘shadow evaporation’ to reduce the number and complexity of the steps required to produce isolated devices and arrays of devices, and eliminates the need for registration (the sequential stacking of patterns with correct alignment) entirely. The defining advantage of this strategy is that it extracts information from the 3D topography of features in photoresist, and combines this information with the 3D information from the angle-dependent deposition (the angle and orientation used for deposition from a collimated source of material), to create ‘shadowed’ and ‘illuminated’ regions on the underlying substrate. It also takes advantage of the ability of replica molding techniques to produce 3D topography in polymeric resists. A single layer of patterned resist can thus direct the fabrication of a nearly unlimited number of possible shapes, composed of layers of any materials that can be deposited by vapor deposition. The sequential deposition of various shapes (by changing orientation and material source) makes it possible to fabricate complex structures—including interconnected transistors—using a single layer of topography. The complexity of structures that can be fabricated using simple lithographic features distinguishes this procedure from other techniques based on shadow evaporation.Publication High-Current-Density Monolayer CdSe/ZnS Quantum Dot Light-Emitting Devices with Oxide Electrodes(Wiley-Blackwell, 2011) Likovich, Edward Michael; Jaramillo, Rafael; Russell, Kasey; Ramanathan, Shriram; Narayanamurti, VenkateshPublication Large spontaneous emission enhancement in plasmonic nanocavities(Nature Publishing Group, 2012) Russell, Kasey; Liu, Tsung-li; Cui, Shanying; Hu, EvelynCavity–emitter coupling can enable a host of potential appli- cations in quantum optics, from low-threshold lasers to brighter single-photon sources for quantum cryptography1. Although some of the first demonstrations of spontaneous emission modification occurred in metallic structures2,3, it was only after the recent demonstration of cavity quantum electrody- namics effects in dielectric optical cavities4 that metal-based optical cavities were considered for quantum optics appli- cations5–13. Advantages of metal–optical cavities include their compatibility with a large variety of emitters and their broad- band cavity spectra, which enable enhancement of spectrally broad emitters. Here, we demonstrate radiative emission rate enhancements approaching 1,000 for emitters coupled to the nanoscale gap between a silver nanowire and a silver substrate. A quantitative comparison of our results with analytical theory shows that the enhanced emission rate of gap-mode plasmons in our structures can yield high internal quantum efficiency despite the close proximity of metal surfaces.Publication Scattering-Assisted Tunneling: Energy Dependence, Magnetic Field Dependence, and Use as an External Probe of Two-Dimensional Transport(American Physical Society, 2010) Russell, Kasey; Capasso, Federico; Narayanamurti, Venkatesh; Lu, H.; Zide, J. M. O.; Gossard, A. C.For more than three decades, research on tunneling through planar barriers has focused principally on processes that conserve momentum parallel to the barrier. Here we investigate transport in which scattering destroys lateral momentum conservation and greatly enhances the tunneling probability. We have measured its energy dependence using capacitance spectroscopy, and we show that for electrons confined in a quantum well, the scattering enhancement can be quenched in an applied magnetic field, enabling this mechanism to function as an external probe of the origin of the quantum Hall effect.Publication Narrow Band Defect Luminescence from AI-doped ZnO Probed by Scanning Tunneling Cathodoluminescence(American Institute of Physics, 2011) Likovich, Edward M.; Jaramillo, Rafael; Russell, Kasey; Ramanathan, Shriram; Narayanamurti, VenkateshWe present an investigation of optically active near-surface defects in sputtered Al-doped ZnO films using scanning tunneling microscope cathodoluminescence (STM-CL). STM-CL maps suggest that the optically active sites are distributed randomly across the surface and do not correlate with the granular topography. In stark contrast to photoluminescence results, STM-CL spectra show a series of sharp, discrete emissions that characterize the dominant optically active defect, which we propose is an oxygen vacancy. Our results highlight the ability of STM-CL to spectrally fingerprint individual defects and contribute to understanding the optical properties of near-surface defects in an important transparent conductor.Publication Measuring the Mode Volume of Plasmonic Nanocavities Using Coupled Optical Emitters(American Physical Society, 2012) Russell, Kasey; Yeung, Yan Mui Kitty; Hu, EvelynMetallic optical systems can confine light to deep subwavelength dimensions, but verifying the level of confinement at these length scales typically requires specialized techniques and equipment for probing the near field of the structure. We experimentally measured the confinement of a metal-based optical cavity by using the cavity modes themselves as a sensitive probe of the cavity characteristics. By perturbing the cavity modes with conformal dielectric layers of subnanometer thickness using atomic layer deposition, we find the exponential decay length of the modes to be less than 5% of the free-space wavelength \((\lambda)\) and the mode volume to be of order \(\lambda^3/1000\). These results provide experimental confirmation of the deep subwavelength confinement capabilities of metal-based optical cavities.Publication Dislocation Density-Dependent Quality Factors in InGaN Quantum Dot Containing Microdisks(American Institute of Physics, 2011) El-Ella, H.A.R.; Rol, F; Kappers, M.J.; Russell, Kasey; Hu, Evelyn; Oliver, R.A.Microdisks incorporating InGaN quantum dots were fabricated using SiO2 microspheres as a hard mask in conjunction with a photoelectrochemical etch step from a structure containing a sacrificial InGaN/InGaN superlattice. Formation of microdisks from two near-identical structures with differing dislocation densities was carried out and investigated using microphotoluminescence. This confirmed the existence of quantum dots through the presence of resolution limited spectral lines and showed a clear correlation between the resulting modes quality factors and the dislocation densities within the disks. The disks with higher dislocation densities showed up to 80% lower quality factors than the low dislocation density disks.Publication Gap-mode Plasmonic Nanocavity(American Institute of Physics, 2010) Russell, Kasey; Hu, EvelynHere we describe the fabrication and characterization of a plasmonic nanocavity formed in the narrow gap between a Ag nanowire and a flat Ag substrate. The fluorescence spectrum of nanocrystals within the gap was strongly modified by the cavity modes, showing peaks of position and width (Q ∼ 30–60) in quantitative agreement with numerical calculations. At gap spacings of ∼ 15 nm, the noncavity background fluorescence is largely quenched by the Ag substrate, while the modal fluorescence remains strong, indicating that gap-type structures are more robust to fluorescence quenching.