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Das P.,Saha Institute of Nuclear Physics | Chini T.K.,Saha Institute of Nuclear Physics | Pond J.,Lumerical Solutions Inc.
Journal of Physical Chemistry C | Year: 2012

We report the spatial maps of the localized surface plasmon resonances associated photon emission in a truncated tetrahedral gold nanoparticle on a silicon substrate. Site-specific cathodoluminescence spectroscopy and imaging in a scanning electron microscope shows stronger photon emission in the visible range near the tips of the particle in contact with the substrate compared to the edges of the particle. Strong local field variations on a length scale as short as 19 nm are resolved. We also perform FDTD simulations of both the spectra and, for the first time, the full cathodoluminescence images. Excellent agreement is obtained with the experimental results, and the detailed information available from the simulated results makes it possible to identify the signature of out-of-plane higher order modes in the truncated tetrahedral gold particle. © 2012 American Chemical Society. Source


Chowdhury M.H.,University of Maryland Baltimore County | Ray K.,University of Maryland Baltimore County | Johnson M.L.,University of Virginia | Gray S.K.,Argonne National Laboratory | And 2 more authors.
Journal of Physical Chemistry C | Year: 2010

There is presently a worldwide effort to increase the speed and decrease the cost of DNA sequencing as exemplified by the goal of the National Human Genome Research Institute (NHGRI) to sequence a human genome for under $1000. Several high throughput technologies are under development. Among these, single strand sequencing using exonuclease appear very promising. However, this approach requires complete labeling of at least two bases at a time, with extrinsic high quantum yield probes. This is necessary because nucleotides absorb in the deep ultraviolet (UV) and emit with extremely low quantum yields. Hence intrinsic emission from DNA and nucleotides is not being exploited for DNA sequencing. In the present paper we consider the possibility of identifying single nucleotides using their intrinsic emission. We used the finite-difference time-domain (FDTD) method to calculate the effects of aluminum nanoparticles on nearby fluorophores that emit in the UV. We find that the radiated power of UV fluorophores is significantly increased when they are in close proximity to aluminum nanostructures. We show that there will be increased localized excitation near aluminum particles at wavelengths used to excite intrinsic nucleotide emission. Using FDTD simulation we show that a typical DNA base when coupled to appropriate aluminum nanostructures leads to highly directional emission. Additionally we present experimental results showing that a thin film of nucleotides show enhanced emission when in close proximity to aluminum nanostructures. Finally we provide Monte Carlo simulations that predict high levels of base calling accuracy for an assumed number of photons that is derived from the emission spectra of the intrinsic fluorescence of the bases. Our results suggest that single nucleotides can be detected and identified using aluminum nanostructures that enhance their intrinsic emission. This capability would be valuable for the ongoing efforts toward the $1000 genome. © 2010 American Chemical Society. Source


Heni W.,ETH Zurich | Haffner C.,ETH Zurich | Baeuerle B.,ETH Zurich | Fedoryshyn Y.,ETH Zurich | And 10 more authors.
Journal of Lightwave Technology | Year: 2016

We report on high-extinction-ratio, ultrafast plasmonic Mach-Zehnder modulators. We demonstrate data modulation at line rates up to 72 Gbit/s (BPSK) and 108 Gbit/s (4-ASK). The driving voltages are Ud = 4 and 2.5 Vp for 12.5 and 25 μm short devices, respectively. The frequency response shows no bandwidth limitations up to 70 GHz. Static characterizations indicate extinction ratios > 25 dB. © 1983-2012 IEEE. Source


A method and apparatus for simulating a mesh element of an anisotropic medium are provided. A unitary transformation is applied to an initial coordinate system of the mesh element by a transformation module to produce a transformed reference coordinate system of the mesh element. Maxwells equations for the mesh element are solved by an update generation module using computational methods to obtain an electric field tensor and an electric displacement field tensor within the mesh element. A unitary transformation to the electric field tensor and the electric displacement tensor are performed by a transformation module to calculate a corresponding electric field tensor and electric displacement tensor for the mesh element in the initial coordinate system.


Wang X.,University of British Columbia | Wang X.,Lumerical Solutions Inc. | Wang Y.,University of British Columbia | Flueckiger J.,University of British Columbia | And 6 more authors.
Optics Letters | Year: 2014

We present waveguide Bragg gratings with misaligned sidewall corrugations on a silicon-on-insulator platform. The grating strength can be tuned by varying the misalignment between the corrugations on the two sidewalls. This approach allows for a wide range of grating coupling coefficients to be achieved with precise control, and substantially reduces the effects of quantization error due to the finite mask grid size. The experimental results are in very good agreement with simulations using the finite-difference time-domain (FDTD) method. © 2014 Optical Society of America. Source

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