Andrew P. Magyar

Homoepitaxial Growth of Single Crystal Diamond Membranes for Quantum Information Processing

Homoepitaxial growth of single crystal diamond membranes is demonstrated employing a microwave plasma chemical vapor deposition technique. The membranes possess excellent structural, optical, and spin properties, which make them suitable for fabrication of optical microcavities for applications in quantum information processing, photonics, spintronics, and sensing.

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 ~

Fabrication of thin, luminescent, single-crystal diamond membranes

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

Coupling of silicon-vacancy centers to a single crystal diamond cavity

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.

The structure–function relationships of a natural nanoscale photonic device in cuttlefish chromatophores

The formation of single-crystal diamond membranes is an important prerequisite for the fabrication of high-quality optical cavities in this material. Diamond membranes fabricated using lift-off processes involving the creation of a damaged layer through ion implantation often suffer from residual ion damage, which severely limits their usefulness for photonic structures. The current work demonstrates that strategic etch removal of the most highly defective material yields thin, single-crystal diamond membranes with strong photoluminescence and a Raman signature approaching that of single-crystal bulk diamond. These optically active membranes can form the starting point for fabrication of high-quality optical resonators.

Silicon-Vacancy Color Centers in Nanodiamonds: Cathodoluminescence Imaging Markers in the Near Infrared

Optical coupling of an ensemble of silicon-vacancy (SiV) centers to single-crystal diamond microdisk cavities is demonstrated. The cavities are fabricated from a single-crystal diamond membrane generated by ion implantation and electrochemical liftoff followed by homo-epitaxial overgrowth. Whispering gallery modes spectrally overlap with the zero-phonon line (ZPL) of the SiV centers and exhibit quality factors ∼ 2200. Lifetime reduction from 1.8 ns to 1.48 ns is observed from SiV centers in the cavity compared to those in the membrane outside the cavity. These results are pivotal in developing diamond integrated photonics networks.

High quality SiC microdisk resonators fabricated from monolithic epilayer wafers

Cuttlefish, Sepia officinalis, possess neurally controlled, pigmented chromatophore organs that allow rapid changes in skin patterning and coloration in response to visual cues. This process of adaptive coloration is enabled by the 500% change in chromatophore surface area during actuation. We report two adaptations that help to explain how colour intensity is maintained in a fully expanded chromatophore when the pigment granules are distributed maximally: (i) pigment layers as thin as three granules that maintain optical effectiveness and (ii) the presence of high-refractive-index proteins—reflectin and crystallin—in granules. The latter discovery, combined with our finding that isolated chromatophore pigment granules fluoresce between 650 and 720 nm, refutes the prevailing hypothesis that cephalopod chromatophores are exclusively pigmentary organs composed solely of ommochromes. Perturbations to granular architecture alter optical properties, illustrating a role for nanostructure in the agile, optical responses of chromatophores. Our results suggest that cephalopod chromatophore pigment granules are more complex than homogeneous clusters of chromogenic pigments. They are luminescent protein nanostructures that facilitate the rapid and sophisticated changes exhibited in dermal pigmentation.

Photoluminescent SiC tetrapods.

We recently demonstrated [ 18 ] multi-color cathodoluminescence (CL) of nanodiamonds as a powerful tool for nanoscale imaging of biological structures. CL is the emission of light by matter as the result of electron bombardment. CL imaging of bulk matter is typically carried out in an electron microscope outfi tted with an optical detector, and is widely used in materials characterization. [ 19 ] However, application of CL to imaging biological structures has been hindered by low photon count rates and rapid signal degradation due to the destruction of biomolecules and organic fl uorophores under electron beam irradiation. [ 20 ] These problems may be overcome with correlated CL and secondary electron (SE) imaging of samples tagged with surface-functionalizable nanoparticles containing defects that are robust under electron beam illumination and emit stable, spectrally distinct CL: e.g., A-band defects and NV centers in nanodiamonds, as well as Ce:LuAG nanophosphors. [ 18 ] In this approach, the CLemitting particles function as color-distinguishable nanoscale markers of targeted epitopes, while the correlated SE image provides high-resolution information about the cellular structure. The combination of nanoscale molecular localization and structural imaging acquired simultaneously and in the same instrument constitutes a uniquely powerful new imaging modality. For applications with large intrinsic CL background, e.g., correlated CL and SE imaging of unfi xed/ living cells in an environmental chamber in a scanning electron microscope (SEM), [ 21 ] it is desirable to use spectrally narrow CL markers with emission peaks at wavelengths distinct from the CL background (such as from proteins, nucleic acid, and fl uorophore-conjugated antibodies, which usually emit CL at short optical wavelengths). [ 22 ] However, many of the nanoparticle species investigated to date have relatively broad (∼100 nm) CL emission spectra at room temperature. [ 20 , 23,24 ] Here, we show that silicon-vacancy (Si-V) color centers [ 25 ] in nanodiamonds provide a promising solution to this challenge. Specifi cally, we demonstrate experimentally that nanodiamonds fabricated to incorporate Si-V color centers provide bright, spectrally narrow (∼5 nm) CL emission in the near-infrared (∼740 nm), which lies within the near-infrared transmission window of biological tissue and is DOI: 10.1002/smll.201303582 Nanodiamonds

Bottom-up engineering of diamond micro- and nano-structures

The exquisite mechanical properties of SiC have made it an important industrial material with applications in microelectromechanical devices and high power electronics. Recently, the optical properties of SiC have garnered attention for applications in photonics, quantum information, and spintronics. This work demonstrates the fabrication of microdisks formed from a p-N SiC epilayer material. The microdisk cavities fabricated from the SiC epilayer material exhibit quality factors of as high as 9200 and the approach is easily adaptable to the fabrication of SiC-based photonic crystals and other photonic and optomechanical devices.

Surface Modifications during a Catalytic Reaction: a Combined APT and FIB/SEM Analysis of Surface Segregation

Recently, significant research efforts have been made to develop complex nanostructures to provide more sophisticated control over the optical and electronic properties of nanomaterials. However, there are only a handful of semiconductors that allow control over their geometry via simple chemical processes. Herein, we present a molecularly seeded synthesis of a complex nanostructure, SiC tetrapods, and report on their structural and optical properties. The SiC tetrapods exhibit narrow line width photoluminescence at wavelengths spanning the visible to near-infrared spectral range. Synthesized from low-toxicity, earth abundant elements, these tetrapods are a compelling replacement for technologically important quantum optical materials that frequently require toxic metals such as Cd and Se. This previously unknown geometry of SiC nanostructures is a compelling platform for biolabeling, sensing, spintronics, and optoelectronics.