Ultrafast wavelength jumping and wavelength adjustment with low current using monolithically integrated FML for long-reach UDWDM-PON

Ultrafast wavelength jumping at optical network units (ONUs) for an access network with frequency modulated lasers (FMLs) is demonstrated. This FML consists of an intracavity tunable phase section and filtering gain section. It provides a total of 4.2 nm tuning range with fast wavelength jumping (2.2 nm in 1 µs) and fast adjustment (1.3 nm in 1.8 ns), providing a candidate for the fast tuning ONU for coherent ultradense wavelength-division multiplexing passive optical networks (WDM-PONs).Peer ReviewedPostprint (author's final draft

The light chain but not the heavy chain of botulinum A toxin inhibits exocytosis from permeabilized adrenal chromaffin cells

The heavy and light chains of botulinum A toxin were separated by anion exchange chromatography. Their intracellular actions were studied using bovine adrenal chromaffin cells permeabilized with streptolysin O. Purified light chain inhibited the Ca2+-stimulated [3H]noradrenaline release with a half-maximal effect at about 1.8 nM. The inhibition was incomplete. Heavy chain up to 28 nM was neither effective by itself nor did it enhance the inhibitory effect of light chain. It is concluded that the light chain of botulinum A toxin contains the functional domain responsible for the inhibition of exocytosis

Experimental and simulation study of 1D silicon nanowire transistors using heavily doped channels

The experimental results from 8 nm diameter silicon nanowire junctionless field effect transistors with gate lengths of 150 nm are presented that demonstrate on-currents up to 1.15 mA/m for 1.0 V and 2.52 mA/m for 1.8 V gate overdrive with an off-current set at 100 nA/m. On- to off-current ratios above 108 with a subthreshold slope of 66 mV/dec are demonstrated at 25 oC. Simulations using drift-diffusion which include densitygradient quantum corrections provide excellent agreement with the experimental results. The simulations demonstrate that the present silicon-dioxide gate dielectric only allows the gate to be scaled to 25 nm length before short-channel effects significantly reduce the performance. If high-K dielectrics replace some parts of the silicon dioxide then the technology can be scaled to at least 10 nm gatelength

Strong exciton-erbium coupling in Si nanocrystal-doped SiO2

Silicon nanocrystals were formed in SiO2 using Si ion implantation followed by thermal annealing. The nanocrystal-doped SiO2 layer was implanted with Er to a peak concentration of 1.8 at. %. Upon 458 nm excitation the sample shows a broad nanocrystal-related luminescence spectrum centered around 750 nm and two sharp Er luminescence lines at 982 and 1536 nm. By measuring the excitation spectra of these features as well as the temperature-dependent intensities and luminescence dynamics we conclude that (a) the Er is excited by excitons recombining within Si nanocrystals through a strong coupling mechanism, (b) the Er excitation process at room temperature occurs at a submicrosecond time scale, (c) excitons excite Er with an efficiency >55%, and (d) each nanocrystal can have at most ~1 excited Er ion in its vicinity

'Spillout' effect in gold nanoclusters embedded in c-Al2O3(0001) matrix

Gold nanoclusters are grown by 1.8 MeV Au^\sup{2+} implantation on c-Al\sub{2}O\sub{3}(0001)substrate and subsequent air annealing at temperatures 1273K. Post-annealed samples show plasmon resonance in the optical (561-579 nm) region for average cluster sizes ~1.72-2.4 nm. A redshift of the plasmon peak with decreasing cluster size in the post-annealed samples is assigned to the 'spillout' effect (reduction of electron density) for clusters with ~157-427 number of Au atoms fully embedded in crystalline dielectric matrix with increased polarizability in the embedded system.Comment: 14 Pages (figures included); Accepted in Chem. Phys. Lett (In Press

NUV/Blue spectral observations of sprites in the 320-460 nm region: N2{\mathrm N_2} (2PG) Emissions

A near-ultraviolet (NUV) spectrograph (320-460 nm) was flown on the EXL98 aircraft sprite observation campaign during July 1998. In this wavelength range video rate (60 fields/sec) spectrographic observations found the NUV/blue emissions to be predominantly N2 (2PG). The negligible level of N2+ (1NG) present in the spectrum is confirmed by observations of a co-aligned, narrowly filtered 427.8 nm imager and is in agreement with previous ground-based filtered photometer observations. The synthetic spectral fit to the observations indicates a characteristic energy of ~1.8 eV, in agreement with our other NUV observations.Comment: 7 pages, 2 figures, 1 table, JGR Space Physics "Effects of Thunderstorms and Lightning in the Upper Atmosphere" Special Sectio

Continuous-wave, multimilliwatt, mid-infrared source tunable across 6.4–7.5 μm based on orientation-patterned GaAs

We report a continuous-wave (cw) source of tunable mid-infrared radiation providing tens of milliwatt of output power in the 6460–7517 nm spectral range. The source is based on difference-frequency generation (DFG) in orientation-patterned (OP)-GaAs pumped by a Tm-fiber laser at 2010 nm and a 1064 nm-Yb-fiber-pumped cw optical parametric oscillator. Using a 25.7-mm-long OP-GaAs crystal, we have generated up to 51.1 mW of output power at 6790 nm, with >40 mW and >20 mW across 32% and 80% of the mid-infrared tuning range, respectively, which is to the best of our knowledge the highest tunable cw power generated in OP-GaAs in this spectral range. The DFG output at maximum power exhibits passive power stability better than 2.3% rms over more than 1 h and a frequency stability of 1.8 GHz over more than 1 min, in high spatial beam quality. The system and crystal performance at high pump powers have been studiedPostprint (published version

Highly dispersive photonic band-gap-edge optofluidic biosensors

Highly dispersive photonic band-gap-edge optofluidic biosensors are studied theoretically. We demonstrate that these structures are strongly sensitive to the refractive index of the liquid, which is used to tune dispersion of the photonic crystal. The upper frequency band-gap edge shifts about 1.8 nm for dn=0.002, which is quite sensitive. Results from transmission spectra agree well with those obtained from the band structure theory.Comment: 12 pages including 7 figure

Highly confined electromagnetic fields in arrays of strongly coupled Ag nanoparticles

Linear arrays of very small Ag nanoparticles (diameter ~10 nm, spacing 0–4 nm) were fabricated in sodalime glass using an ion irradiation technique. Optical extinction spectroscopy of the arrays reveals a large polarization-dependent splitting of the collective plasmon extinction band. Depending on the preparation condition, a redshift of the longitudinal resonance as large as 1.5 eV is observed. Simulations of the three-dimensional electromagnetic field evolution are used to determine the resonance energy of idealized nanoparticle arrays with different interparticle spacings and array lengths. Using these data, the experimentally observed redshift is attributed to collective plasmon coupling in touching particles and/or in long arrays of strongly coupled particles. The simulations also indicate that for closely coupled nanoparticles (1–2 nm spacing) the electromagnetic field is concentrated in nanoscale regions (10 dB radius: 3 nm) between the particles, with a 5000-fold local field intensity enhancement. In arrays of 1-nm-spaced particles the dipolar particle interaction extends to over 10 particles, while for larger spacing the interaction length decreases. Spatial images of the local field distribution in 12-particle arrays of touching particles reveal a particlelike coupled mode with a resonance at 1.8 eV and a wirelike mode at 0.4 eV