Dynamics of elliptical beams in the anomalous group-velocity dispersion regime.

We investigate 3D spatio-temporal focusing of elliptically-shaped beams in a bulk medium with Kerr nonlinearity and anomalous group-velocity dispersion (GVD). Strong space-time localization of the mode is observed through multi-filamentation with temporal compression by a factor of 3. This behavior is in contrast to the near-zero GVD regime in which minimal pulse temporal compression is observed.

Filamentation in air with ultrashort mid-infrared pulses.

We theoretically investigate filamentation of ultrashort laser pulses in air in the mid-infrared regime under conditions in which the group-velocity dispersion (GVD) is anomalous. When a high-power, ultra-short mid-infrared laser beam centered at 3.1-μm forms a filament, a spatial solitary wave is stabilized by the plasma formation and propagates several times its diffraction length.

Spectral amplitude and phase measurement of ultrafast pulses using all-optical differential tomography.

We demonstrate a simple, all-optical, fiber-based method for characterizing the spectral amplitude and phase of ultrafast pulses using a differential tomographic measurement realized via four-wave mixing. The technique is applied to subpicosecond pulses in the C-band of the telecommunication spectrum. Characterization of amplified pulses and propagation through dispersive media is demonstrated and compared with autocorrelation measurements and calculated predictions.

Long-term enzyme replacement therapy in a severe case of mucopolysaccharidosis type II (Hunter syndrome).

Hunter syndrome or mucopolysaccharidosis II (MPS II) is a rare X-linked disease caused by a deficiency of the iduronate-2-sulphatase (12S) lysosomal enzyme, resulting in a progressive accumulation of glycosaminoglycans (GAGs). Enzyme replacement therapy (ERT) with recombinant human 12S idursulfase has been used infrequently in children < 5 years. We present the case of a 7 years and 10 months-old child, who was diagnosed with a severe form of MPS II at the age of 3 years, and who began a 36 months' treatment with idursulfase at 4 years 10 months.

All-optical switching of a single resonance in silicon ring resonators.

We theoretically investigate a wavelength-selective all-optical switch using Raman-induced loss in a silicon resonator add-drop filter. We show that picojoule control pulses can selectively modulate and "erase" a single cavity resonance from full extinction to greater than 97% transmission while leaving adjacent resonances undisturbed. Full switching is achievable in less than 300 ps with only a few hundred femtojoule energy dissipation.

Continuous-wave mid-infrared frequency conversion in silicon nanowaveguides.

We report the first demonstration of cw wavelength conversion from the telecommunications band to the mid-IR (MIR) region via four-wave mixing in silicon nanowaveguides. We measure a parametric bandwidth of 748 nm by converting a 1636 nm signal to produce a 2384 nm idler and show continuously tunable wavelength conversion from 1792 to 2116 nm. This report indicates that the advantages of silicon photonics may be leveraged to create devices for a large range of MIR applications that require cw operation.

Synthesis, physical-chemical characterisation and biological evaluation of novel 2-amido-3-hydroxypyridin-4(1H)-ones: Iron chelators with the potential for treating Alzheimer's disease.

A novel class of 2-amido-3-hydroxypyridin-4-one iron chelators is described. These compounds have been designed to behave as suitable molecular probes which will improve our knowledge of the role of iron in neurodegenerative conditions. Neurodegenerative disorders, such as Alzheimer's disease (AD) and Parkinson disease (PD), can be considered as diverse pathological conditions sharing critical metabolic processes such as protein aggregation and oxidative stress.

Wide-bandwidth continuously tunable optical delay line using silicon microring resonators.

We demonstrate a distortion free tunable optical delay as long as 135 ps with a 10 GHz bandwidth using thermally tuned silicon microring resonators in the novel balanced configuration. The device is simple, easy to control and compact measuring only 30 µm wide by 250 µm long.

Wavelength multicasting in silicon photonic nanowires.

We demonstrate a scalable, energy-efficient, and pragmatic method for high-bandwidth wavelength multicasting using FWM in silicon photonic nanowires. We experimentally validate up to a sixteen-way multicast of 40-Gb/s NRZ data using spectral and temporal responses, and evaluate the resulting data integrity degradation using BER measurements and power penalty performance metrics. We further examine the impact of this wavelength multicasting scalability on conversion efficiency.

All-optical modulation of four-wave mixing in an Rb-filled photonic bandgap fiber.

We demonstrate efficient all-optical modulation using Rb vapor confined to a hollow-core photonic bandgap fiber. The intensity of a signal field participating in the four-wave-mixing process is modulated using a weak switching field. We observe 3 dB of attenuation in the signal field with only 3600 photons of switching energy, corresponding to 23 photons per atomic cross section lambda(2)/(2pi).

Temporal-imaging system with simple external-clock triggering.

We demonstrate a temporal imaging system based on parametric mixing that allows simple triggering from an external clock by using a time-lens-based pump laser. We integrate our temporal imaging system into a time-to-frequency measurement scheme and demonstrate the ability to perform characterization of temporal waveforms with 1.4-ps resolution and a 530-ps record length.

Use of 2-[(18)F]fluoroethylazide for the Staudinger ligation - Preparation and characterisation of GABA(A) receptor binding 4-quinolones.

The labelling reagent 2-[(18)F]fluoroethylazide was used in a traceless Staudinger ligation. This reaction was employed to obtain the GABA(A) receptor binding 6-benzyl-4-oxo-1,4-dihydro-quinoline-3-carboxylic acid (2-[(18)F]fluoroethyl) amide. The radiotracer was prepared with a non-decay corrected radiochemical yield of 7%, a radiochemical purity >95% and a specific radioactivity of 0.

Ultrashort free-carrier lifetime in low-loss silicon nanowaveguides.

We demonstrate reduction of the free-carrier lifetime in a silicon nanowaveguide from 3 ns to 12.2 ps by applying a reverse bias across an integrated p-i-n diode. This observation represents the shortest free-carrier lifetime demonstrated to date in silicon waveguides.

Highly-efficient coupling of linearly- and radially-polarized femtosecond pulses in hollow-core photonic band-gap fibers.

We demonstrate extremely efficient excitation of linearly-, radially-, and azimuthally-polarized modes in a hollow-core photonic band-gap fiber with femtosecond laser pulses. We achieve coupling efficiencies as high as 98% with linearly polarized input Gaussian beams and with high-power pulses we obtain peak intensities greater than 10(14) W/cm(2) inside and transmitted through the fiber. With radially polarized pulses, we achieve 91% total transmission through the fiber while maintaining the polarization state.

Frequency conversion over two-thirds of an octave in silicon nanowaveguides.

We demonstrate ultrabroad-bandwidth low-power frequency conversion of continuous-wave light in a dispersion engineered silicon nanowaveguide via four-wave mixing. Our process produces continuously tunable four-wave mixing wavelength conversion over two-thirds of an octave from 1241-nm to 2078-nm wavelength light with a pump wavelength in the telecommunications C-band.

Ultralong continuously tunable parametric delays via a cascading discrete stage.

We report experimental demonstration of an all-optical continuously tunable delay line based on parametric mixing with a total delay range of 7.34 mus. The bit-error rate performance of the delay line was characterized for a 10-Gb/s NRZ data channel.

Diagnosis of neurological herpesvirus infections: real time PCR in cerebral spinal fluid analysis.

Human herpesviruses (HHVs) cause many serious acute and persistent central nervous system (CNS) disorders. Because these infections manifest with various, often non-specific, symptoms and signs, and because specific therapy is often available, accurate diagnosis is essential. Cerebrospinal fluid (CSF) from 146 patients with acute meningitis or meningoencephalitis and 9 with "other neurological disorders" were analyzed by using an automatic system for nucleic acid extraction and quantitative real-time polymerase chain reaction (PCR) for herpes simplex 1 and 2 (HSV-1, HSV-2), Epstein-Barr virus (EBV), human cytomegalovirus (HCMV), herpesvirus-6 (HHV-6), and varicella-zoster virus (VZV).

Spectral phase conjugation via temporal imaging.

We experimentally demonstrate wavelength-preserving spectral phase conjugation for compensating chromatic dispersion and self-phase modulation in optical fibers. Our implementation is based on a temporal imaging scheme that uses time lenses realized by broadband four-wave mixing in silicon waveguides. By constructing a temporal analog of a 4-f imaging system, we compensate for pulse distortions arising from second- and third-order dispersion and self-phase modulation in optical fibers.

Theoretical and experimental investigation of broadband cascaded four-wave mixing in high-Q microspheres.

We analyze the process of cascaded four-wave mixing in a high-Q microcavity and show that under conditions of suitable cavity-mode dispersion, broadband frequency combs can be generated. We experimentally demonstrate broadband, cascaded four-wave mixing parametric oscillation in the anomalous group-velocity dispersion regime of a high-Q silica microsphere with an overall bandwidth greater than 200 nm.

Ultralow-power four-wave mixing with Rb in a hollow-core photonic band-gap fiber.

We demonstrate extremely efficient four-wave mixing with gains greater than 100 at microwatt pump powers and signal-to-idler conversion of 50% in Rb vapor confined to a hollow-core photonic band-gap fiber. We present a theoretical model that demonstrates such efficiency is consistent with the dimensions of the fiber and the optical depths attained. This is, to our knowledge, the largest four-wave mixing gain observed at such low total pump powers and the first demonstrated example of four-wave mixing in an alkali-metal vapor system with a large (approximately 30 MHz) ground state decoherence rate.

Generation of large alkali vapor densities inside bare hollow-core photonic band-gap fibers.

We demonstrate the ability to generate extremely large rubidium densities in uncoated hollow-core photonic band-gap fibers using light-induced atomic desorption. Once the fiber is exposed to Rb vapor for 1-2 weeks, and this atomic source is removed, the fiber yields large desorbable densities for an extended period of time. We show that optical depths greater than e(-1200) can be created within seconds.

1 micros tunable delay using parametric mixing and optical phase conjugation in Si waveguides.

We demonstrate continuously tunable optical delays as large as 1.1 micros range for 10 Gb/s NRZ optical signals based on four-wave mixing (FWM) process in silicon waveguide. The large delay range is made possible by a novel wavelength-optimized optical phase conjugation scheme, which allows for tunable dispersion compensation to minimize the residual group-velocity dispersion (GVD) for the entire tuning range.

Silicon-waveguide-coupled high-Q chalcogenide microspheres.

We fabricate high-Q arsenic triselenide glass microspheres through a three-step resistive heating process. We demonstrate quality factors greater than 2 x 10(6) at 1550 nm and achieve efficient coupling via a novel scheme utilizing index-engineered unclad silicon nanowires. We find that at powers above 1 mW the microspheres exhibit high thermal instability, which limits their application for resonator-enhanced nonlinear optical processes.

High-resolution spectroscopy using a frequency magnifier.

We experimentally demonstrate a spectral magnifier using an imaging system with two time-lenses based on four-wave mixing in a Si nanowaveguide. We achieve a magnification factor of 105 with a frequency resolution of 1 GHz. The system offers potential as a tool for single-shot, high resolution spectral measurements.

High-speed optical sampling using a silicon-chip temporal magnifier.

We demonstrate a single-shot technique for optical sampling based on temporal magnification using a silicon-chip time lens. We demonstrate the largest reported temporal magnification factor yet achieved (>500) and apply this technique to perform 1.3 TS/s single-shot sampling of ultrafast waveforms and to 80-Gb/s performance monitoring.