Inducing photonic transitions between discrete modes in a silicon optical microcavity

We show the existence of direct photonic transitions between modes of a silicon optical microcavity spaced apart in wavelength by over 8 nm. This is achieved by using ultrafast tuning of the refractive index of the cavity over a time interval that is comparable to the inverse of the frequency separation of modes. The demonstrated frequency mixing effect, i.e., the transitions between the modes, would enable on-chip silicon comb sources which can find wide applications in optical sensing, precise spectroscopy, and wavelength-division multiplexing for optical communications and interconnects.     

High-speed electro-optic control of the optical quality factor of a silicon microcavity

We demonstrate electro-optic ultrafast control of the optical quality factor of an on-chip silicon microcavity. The micrometer-sized cavity is formed by light confinement between two microring resonators acting as frequency selective mirrors. The ring resonators are integrated into p-i-n junctions enabling ultrafast injection and extraction of carriers. We show tuning of the cavity quality factor from 20,000 to 6,000 in under 100 ps. We demonstrate both high-Q to low-Q and low-Q to high-Q transitions.     

Wide temperature range operation of micrometer-scale silicon electro-optic modulators

We demonstrate high bit rate electro-optic modulation in a resonant micrometer-scale silicon modulator over an ambient temperature range of 15 K. We show that low bit error rates can be achieved by varying the bias current through the device to thermally counteract the ambient temperature changes. Robustness in the presence of thermal variations can enable a wide variety of applications for dense on chip electronic photonic integration.     

Paramagnetic centers in single-walled carbon nanotubes encapsulated with palladium and their interaction with hydrogen at H/C ≥ 1.0

The nature of paramagnetic centers in a nanostructure based on single-walled carbon nanotubes (SWCNTs) encapsulated with Pd was studied by EPR spectroscopy at 77 and 293 K. It was found that strong charge-transfer π complexes of the (Pd-C _x ) type, which manifested themselves as a narrow resonance (ΔH = 6–8 G and g = 2.002 at T = 77 k), were formed in the Pd-SWCNT composite along with impurity centers (Fe₃O₄ nanoparticles within the nanotubes), which were responsible for a broad EPR signal (ΔH = 75 G and g = 2.065 at T = 293 K). These complexes were found to be predominant adsorption sites responsible for a high gravimetric density of hydrogen (H/C ≥ 1.0) within the single-walled carbon nanotubes.     

Production of radially and azimuthally polarized polychromatic beams

We describe a system that efficiently provides radially or azimuthally polarized radiation from a randomly polarized source. It is constructed from two conical reflectors and a cylindrical sheet of polarizing film. Envisaged applications include a microscope illuminator for high-resolution surface plasmon resonance microscopy, illumination for high-resolution microlithography, and efficient coupling of a laser source to hollow optical fibers. The angular coherence function of light polarized by the device was measured to evaluate its usefulness for these applications.     

α,β-Unsaturated ketones based on allobetulone

Crotonization of allobetulone with aromatic and heteroaromatic aldehydes gave a number of new α,β-unsaturated ketones of the lupane series, and their steric structure was determined by X-ray analysis of (E)-4-[(3-oxoallobetulan-2-ylidene)methyl]benzonitrile as an example.     

On the initiation of DD reactions in the zirconium-deuterium system

The possibility of initiating DD reactions on vibro-milling of zirconium together with heavy water and deuterated polypropylene has been investigated. Weak emission of neutrons has been detected both during the vibro-milling process and some time after its completion.