Kasey J. Russell

Deterministic coupling of delta-doped nitrogen vacancy centers to a nanobeam photonic crystal cavity

The negatively-charged nitrogen vacancy center (NV) in diamond has generated significant interest as a platform for quantum information processing and sensing in the solid state. For most applications, high quality optical cavities are required to enhance the NV zero-phonon line (ZPL) emission. An outstanding challenge in maximizing the degree of NV-cavity coupling is the deterministic placement of NVs within the cavity. Here, we report photonic crystal nanobeam cavities coupled to NVs incorporated by a delta-doping technique that allows nanometer-scale vertical positioning of the emitters. We demonstrate cavities with Q up to ~24,000 and mode volume V ~

Low threshold, room-temperature microdisk lasers in the blue spectral range

0.47({\lambda}/n)^{3}

Room-temperature electro-optic up-conversion via internal photoemission

as well as resonant enhancement of the ZPL of an NV ensemble with Purcell factor of ~20. Our fabrication technique provides a first step towards deterministic NV-cavity coupling using spatial control of the emitters.

Growth of ZnO nanowires catalyzed by size-dependent melting of Au nanoparticles.

InGaN-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/cm2. 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

Gap-mode Plasmonic Nanocavity

We describe the fabrication and operation of a device which performs linear optical up-conversion at room temperature. The mechanism for up-conversion is based on internal photoemission from a Schottky contact. We then describe the voltage dependence of this device and interpret it in terms of total energy conservation. Although an AlGaAs/GaAs system is employed here, the functionality is not material-specific and therefore should be widely applicable to different materials systems, such as GaN/InGaN.

High-Current-Density Monolayer CdSe/ZnS Quantum Dot Light-Emitting Devices with Oxide Electrodes

We present a general approach to growing ZnO nanowires on arbitrary, high melting point (above 970 degrees C) substrates using the vapor-liquid-solid (VLS) growth mechanism. Our approach utilizes the melting point reduction of sufficiently small (5 nm diameter) Au particles to provide a liquid catalyst without substrate interaction. Using this size-dependent melting effect, we demonstrate catalytic VLS growth of ZnO nanowires on both Ti and Mo foil substrates with aspect ratios in excess of 1000:1. Transmission electron microscopy shows the nanowires to be single-crystalline, and photoluminescence spectra show high-quality optical properties. We believe this growth technique to be widely applicable to a variety of substrates and material systems.

Narrow band defect luminescence from Al-doped ZnO probed by scanning tunneling cathodoluminescence

Here 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.

Room-temperature ballistic electron emission luminescence spectroscopy with a scanning tunneling microscope

Films of semiconductor quantum dots (QDs) are promising for lighting technologies, but controlling how current flows through QD films remains a challenge. A new design for a QD light-emitting device that uses atomic layer deposition to fill the interstices between QDs with insulating oxide is introduced. It funnels current through the QDs themselves, thus increasing the light emission yield.

Two-dimensional hybrid photonic/plasmonic crystal cavities

We 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.

Ballistic electron emission luminescence

We present a luminescence spectroscopy for semiconductor heterostructures based on local hot electron injection from a scanning tunneling microscope tip. In addition to a tip voltage bias exceeding the metal-semiconductor Schottky barrier height, this process requires a collector bias voltage to satisfy energy conservation. These results indicate that this method could be used to study local electron transport and simultaneous electroluminescence in buried luminescent layers at depths greater than the ballistic electron mean free path in the collector.