Narrow-Linewidth Distributed Feedback Channel Waveguide Laser in Al2_2O3_3:Er3+^{3+}

We report on the fabrication and characterization of a distributed feedback channel waveguide laser in erbium-doped aluminium oxide on a standard thermally oxidized silicon substrate. Holographically-written surface-relief Bragg gratings have been integrated with the aluminium oxide waveguides via reactive ion etching of a silicon dioxide overlay film. The laser operates at a wavelength of 1545.2 nm and exhibits a threshold of 2.2 mW absorbed pump power, while it produces a maximum output power of 3 mW. The emission is TE polarized and has a Lorentzian linewidth of 1.70±0.58 kHz, which corresponds to a Q-factor of 1.14×E11

Far-field scattering microscopy applied to analysis of slow light, power enhancement, and delay times in uniform Bragg waveguide gratings

A novel method is presented for determining the group index, intensity enhancement and delay times for waveguide gratings, based on (Rayleigh) scattering observations. This far-field scattering microscopy (FScM) method is compared with the phase shift method and a method that uses the transmission spectrum to quantify the slow wave properties. We find a minimum group velocity of 0.04c and a maximum intensity enhancement of ~14.5 for a 1000-period grating and a maximum group delay of ~80 ps for a 2000-period grating. Furthermore, we show that the FScM method can be used for both displaying the intensity distribution of the Bloch resonances and for investigating out of plane losses. Finally, an application is discussed for the slow-wave grating as index sensor able to detect a minimum cladding index change of $10^{-8}$, assuming a transmission detection limit of $10^{-4}$

Line-Defect Waveguides in Hexagon-Hole type Photonic Crystal Slabs: Design and Fabrication using Focused Ion Beam Technology

Photonic-crystal slabs (PCS) patterned with a 2D triangular-lattice having hexagonal holes rotated with respect to their symmetry axis can provide a larger bandgap than similar slabs with circular holes. A step forward towards integrated optical devices is introducing line ‘defects’ in PCS, the goal being the achievement of single-mode waveguiding over a frequency range as large as possible, inside the gap. We present the design for defect waveguides with reduced width and a novel fabrication technique, which is an integration of optical lithography with focused ion beam (FIB) high-resolution etching. This technique allows a good alignment between a line ‘defect’ and conventional ridge waveguides

Dose- and Time-Dependent Increase of Lysosomal Enzymes in Embryonic Cartilage in Vitro after Ionizing Radiation

Radiation doses of 20, 50 or 100 Gy caused the same time related decrease for RNA and proteoglycan (PG) synthesis in embryonic cartilage in vitro (4 days culture). In this paper, participation of lysosomes in this radiation response is investigated. Therefore, we employ a cytochemical method using -glycerophosphate as substrate for acid phosphatase (AP) detection. Increase of AP was found 2 days after irradiation and increased during the whole culture period. The increase was more pronounced with a higher radiation dose. Stimulation of AP activity explains the observed radiation response of RNA and PG synthesis

Effects of Ionizing Radiation on Cartilage: Emphasis on Effects on the Extracellular Matrix

In this report, we review data dealing with radiation effects on cartilage. More specifically, we emphasize on alterations caused in the extra-cellular cartilage matrix. Although radiation studies predominantly describe the effect on the structure of DNA and on the mitotic activity of cells, alterations caused by the effect on the non-mitotic activity can also be important. Cartilage, having an extracellular matrix composed of 2 major components, aggrecan and collagen, provides a good model to study this kind of radiation effects. The following topics concerning literature data are summarized: effects on the amount of matrix synthesized, effects on the activity of certain enzymes and effects on the structure and morphology of the matrix. Some new findings concerning the radiation effect on the size distribution of aggrecan-aggregate populations, de novo synthesized by chondrocyte cultures, either derived from calcifying or from non-calcifying cartilage, are given

NNLO QCD corrections to event shape variables in electron positron annihilation

Precision studies of QCD at electron-positron colliders are based on measurements of event shapes and jet rates. To match the high experimental accuracy, theoretical predictions to next-to-next-to-leading order (NNLO) in QCD are needed for a reliable interpretation of the data. We report the first calculation of NNLO corrections O(alpha_s^3) to three-jet production and related event shapes, and discuss their phenomenological impact.Comment: Contributed to 2007 Europhysics Conference on High Energy Physics, Manchester, England 19-25 July 200

Effects of Ionizing Radiation on the Size Distribution of Proteoglycan Aggregates Synthesized by Chondrocytes in Agarose

Effects of ionizing radiation on the structure and size-distribution of newly synthesized proteoglycan aggregates are studied in-vitro. Chondrocytes, isolated from embryonic chick sterna, are cultured for 7 days in a tri-dimensional agarose system. Single radiation doses of 10, 20 and 50 Gy are given before starting the culture. Digestion of the artificial agarose matrix liberates the newly synthesized proteoglycans. Spreading with cytochrome C allows electron microscopic investigations of the individual, newly synthesized molecules. The structure of aggregates synthesized by control and irradiated chondrocytes is comparable. However, radiation causes alterations in the size-distributions of the aggregate-populations. For the control cultures, an average aggregate contains 27 aggrecans per aggregate. 34 pro mille of the molecules contain more than 100 aggrecans per aggregate. Irradiation with 10 Gy doesn\u27t cause alterations. With radiation doses of 20 and 50 Gy, an average molecule contains 20 aggrecans. Only about 9 pro mille of the aggregates contain more than 100 aggrecans. Stimulation of lysosomal activity after irradiation could explain the observed alterations

The infrared structure of e+ e- --> 3 jets at NNLO reloaded

This paper gives detailed information on the structure of the infrared singularities for the process e+ e- --> 3 jets at next-to-next-to-leading order in perturbation theory. Particular emphasis is put on singularities associated to soft gluons. The knowledge of the singularity structure allows the construction of appropriate subtraction terms, which in turn can be implemented into a numerical Monte Carlo program.Comment: 59 pages, additional comments added, version to be publishe

Single-Frequency, Narrow-Linewidth Distributed Feedback Waveguide Laser in Al2O3:Er3+ on Silicon

A distributed feedback channel waveguide laser in erbium-doped aluminum oxide on a silicon substrate is reported. The optically pumped laser has a threshold pump power of 15 mW and emits 3 mW in single-frequency operation at 1545.2 nm wavelength with a slope efficiency of 6.2% and linewidth of 15 kHz