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P.J.A. Sazio,
A. Amezcua-Correa, C.E. Finlayson,
J.R. Hayes,
T.J. Scheidemantel,
N.F. Baril,
B.R. Jackson,
Dong-Jin Won,
Feng Zhang,
E.R. Margine,
V. Gopalan,
V.H. Crespi,
J.V. Badding
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ABSTRACT: Functional materials such as bulk crystalline semiconductor structures inside MOF waveguides could lead to fibre devices with radically new electronic and photonic degrees of freedom. We report the growth of such materials inside MOF templates via a novel microfluidic high pressure chemical vapour deposition technique.
IEEE/LEOS Winter Topical Meeting Series, 2008; 02/2008
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Advanced Functional Materials 07/2007; 17(13):2024 - 2030. · 10.18 Impact Factor
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ABSTRACT: Extreme aspect ratio tubes and wires of polycrystalline silicon and germanium have been deposited within silica microstructured optical fibers using high-pressure precursors, demonstrating the potential of a platform technology for the development of in-fiber optoelectronics. Microstructural studies of the deposited material using Raman spectroscopy show effects due to strain between core and cladding and the presence of amorphous and polycrystalline phases for silicon. Germanium, in contrast, is more crystalline and less strained. This in-fiber device geometry is utilized for two- and three-terminal electrical characterization of the key parameters of resistivity and carrier type, mobility and concentration. (c) 2007 American Institute of Physics.
Applied Physics Letters 01/2007; 90(13). · 3.84 Impact Factor
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ABSTRACT: We report the synthesis of solvent-stabilized lead-iodide nanoparticles, using a convenient route involving coordinating solvents. The resultant colloids show strong absorption features in the ultraviolet region of the optical spectrum, which are consistent with the formation of semiconducting nanocrystals of lead (II) iodide. An effective-mass approximation model of quantum-confined states is in good agreement with the observed transition energies, giving strong indications of the particle morphologies and dimensions. Intense photoluminescence is also observed, with some spectral tuning possible with ripening time, giving a range of emission photon energies approximately spanning from 2.5 to 3.0 eV. We measure photo-stable luminescence quantum efficiencies of around 20% in solution, increasing to up to 30% if the coordinating ligand is exchanged for a Lewis-base capping layer. This demonstrates the potential for the utilization of lead-iodide nanocrystals in visible optoelectronics applications.
Journal of Physics D Applied Physics 03/2006; 39(8):1477. · 2.54 Impact Factor
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ABSTRACT: We report time-of-flight experiments on photonic-crystal waveguide structures using optical Kerr gating of a femtosecond white-light supercontinuum. These photonic-crystal structures, based on engineered silicon-nitride slab waveguides, possess broadband low-loss guiding properties, allowing the group velocity dispersion of optical pulses to be directly tracked as a function of wavelength. This dispersion is shown to be radically disrupted by the spectral band gaps associated with the photonic-crystal periodicity. Increased time-of-flight effects, or "slowed light," are clearly observed at the edges of band gaps in agreement with two-dimensional plane-wave theoretical models of group velocity dispersion. A universal model for slow light in such photonic crystals is proposed, which shows that slow light is controlled predominantly by the detuning from, and the size of, the photonic band gaps. Slowed light observed up to time delays of approximately 1 ps, corresponds to anomalous dispersion of approximately 3.5 ps/nm per mm of the photonic crystal structure. From the decreasing intensity of time-gated slow light as a function of time delay, we estimate the characteristic losses of modes which are guided in the spectral proximity of the photonic band gaps.
Physical Review E 02/2006; 73(1 Pt 2):016619. · 2.26 Impact Factor
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ABSTRACT: We report the selective chemical attachment of infrared emitting PbSe nanocrystal quantum dots onto micron-scale glass photonic beads. Upon optical excitation, photoluminescence from the shell of nanocrystals is seen to couple into the high-Q 'whispering gallery' modes of the bead via the evanescent optical field, resulting in a series of sharp peaks being observed at wavelengths of around 1550 nm. Theoretical modelling gives a close agreement with the data for angular modes corresponding to l ~ 120. This work demonstrates the potential of narrow-bandgap II–VI semiconductor nanocrystals for use in a wide range of telecommunications-window photonics applications.
Semiconductor Science and Technology 01/2006; 21(3):L21. · 1.72 Impact Factor
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ABSTRACT: We have synthesised arrays of semiconductor wires and tubes inside microstructured optical fibres. These extreme aspect ratio structures have highly functional optoelectronic properties and initial characterisation studies of their waveguiding properties are presented here.
Lasers and Electro-Optics Society, 2005. LEOS 2005. The 18th Annual Meeting of the IEEE; 11/2005
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ABSTRACT: We report the incorporation of thin films of a cyanine dye J aggregate into a versatile, length tunable, optical microcavity. The dense J-aggregate layers give an optical response that can be modified by embedding them at specific positions within heterostructures of dielectric and metal layers. The microcavities are composed of separate gold mirrors, which can be individually nanopositioned, and give sharp resonant modes in the red/near-infrared region of the spectrum. With the dye layer favorably placed, anticrossing behavior is observed as the cavity modes are successively swept through the absorption resonance. Large Rabi splittings of up to 170 meV are achieved at room temperature, agreeing well with predictions from a transfer-matrix model. These strongly coupled microcavities pave the way for microelectromechanical systems-integrated microdevices with tailored nonlinear optical properties.
Applied Physics Letters 01/2005; 86(4):041110-041110-3. · 3.84 Impact Factor
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ABSTRACT: We report ultrabroadband measurements on waveguides of photoluminescent silicon-rich silicon dioxide produced by plasma enhanced chemical vapor deposition. Material absorption below 700 nm and waveguide loss above 1300 nm leave a broad spectral region of good transmission properties, which overlaps with the photoluminescence spectrum of the core material. Proposed mechanisms for the material absorption and photoluminescence are discussed based on our findings. © 2003 American Institute of Physics.
Applied Physics Letters 11/2003; 83(22):4598-4600. · 3.84 Impact Factor
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ABSTRACT: Ultrafast optical gating was used to resolve the time of flight of photons through photonic crystal waveguides. We observed the slowing down of light around the band gap.
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ABSTRACT: We demonstrate that ultrabroadband ultrashort-pulse white light supercontina can be used to track the group velocity of photons in optical waveguides using a Kerr gate technique. Results on silicon nitride slab waveguides show both polarization birefringence and multimode dispersion, which vanish at critical wavelengths. When photonic crystals are embedded in the waveguides, the higher order modes are excited within the band-gap region, demonstrating the need to control their dispersion to make effective use of photonic crystal waveguide devices.
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ABSTRACT: Self-phase modulation has been observed for ultrashort pulses of wavelength 800nm propagating through a 1 cm-long Ta2O5 rib waveguide. The associated nonlinear refractive index n2 was estimated to be 7.23x10−19 m2/W, which is higher than silica glass by more than one order of magnitude. Femtosecond time of flight measurements based on a Kerr shutter configuration show that the group velocity dispersion is small at a wavelength of 800 nm, confirming that dispersion may be neglected in the estimation of n2 so that a simplified theory can be used with good accuracy.
