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We present a self-consistent design optimization for nonlinear antiresonant optical waveguides with quasi-phase-matched AlxGa1−xAs multilayer cores. Design parameters for efficient surface normal second-harmonic generation at green and blue wavelengths are obtained.

Quasi-phase-matched second-harmonic (SH) generation in reflection geometry is described and demonstrated. The SH intensity can be strongly enhanced by spatially modulating the optical properties of the nonlinear medium. This type of quasi-phase-matching is demonstrated by using an Al0.8Ga0.2As/GaAs heterostructure designed for λ = 1.06 μm incident light. The SH light intensity generated in reflection from the heterostructure is enhanced 70 times relative to the SH response of a homogeneous GaAs wafer. A resonant cavity design that employs this structure to make thin films with extremely high SH generation efficiencies is proposed.

Active surface-emitting harmonic generators based on monolithic integration of InGaAs/GaAs single-quantum-well (SQW) lasers with multilayered nonlinear waveguides have been fabricated. Wavelength tuning of the integrated SQW laser in active/passive segmented devices has been investigated and used to control the emission angle of the harmonic light for application as spatially addressable coherent detectors.

The SOS chromotest is a simple quantitative short-term bacterial assay for the detection of genotoxic activity of pure compounds or complex samples. On the basis of consecutive experiments aimed at demonstrating the relationship between the inoculum size and the outcome of the test using 4-nitroquinoline-1-oxide (4-NQO) as model genotoxin. It is shown that within the suitable range of the cell number there is a negative correlation between the number of tester cells and test sensitivity. Moreover, it could be demonstrated that the peak of the dose response curve, i.e., the maximal induction factor, is systematically influenced by the actual value of the ratio of beta-galactosidase to alkaline phosphatase enzyme activities at a 4-NQO concentration of zero. Last but not least, some simple statistical data describing the performance of the automated version of the SOS chromotest are also given.

Summary The SOS chromotest is a simple quantitative short-term bacterial assay for the detection of genotoxic activity of pure chemicals or complex samples. The test is based on the measurement of the induction of the SOS response by xenobiotics which cause damage in replicating or non replicating DNA. The assay has been originally developed as a test-tube method but has recently been modified and extensively evaluated ( Quillardet and Hofnung 1985, Quillardet et al. 1985). In an attempt to automate the SOS chromotest a manual test procedure based on microtiter plates (Orgenics Ltd. 1986) has been further adapted to Bioscreen analyzer system (Labsystems OY, Helsinki, Finland). In this application the test is controlled by a self-contained, interactive programme and makes use of a kinetic measure principle for quantifying the enzymatic activities to be evaluated. The present experiences with the automated version of the SOS chromotest indicate its usefulness as primary screening method or part of a battery of bacterial short-term tests for genotoxins and point out its remarkable practical advantages.

Subwavelength structures in silicon waveguides are presented, including practical components such as fiber-chip grating couplers, waveguide crossings, a polarization converter, a waveguide multiplexer and a Terahertz optical switch.

We demonstrate all-optical time division demultiplexing from 160Gb/s to 10Gb/s in the C-band, based on four-wave mixing (FWM) in a silicon nanowire. We achieve error-free operation with a system penalty of ∼ 3.9dB at 10–9 BER.

We report our advances in development of subwavelength engineered metamaterial structures in silicon waveguides, specifically high-efficiency fiber-chip couplers, ultra-broadband surface grating couplers and nanophotonic beam splitters, evanescent field waveguide sensors and on-chip Fourier-transform spectrometers.

A silicon waveguide evanescent field molecular sensor interrogated by reflection from a surface grating is demonstrated. The sensor is probed by a beam of light incident at θ = 45° through the backside of the silicon-on-insulator (SOI) wafer. The reflected power shows a strong resonant feature near λ = 1532 nm, arising from resonant coupling of incident beam, guided mode, and the reflected beam. The resonant wavelength is very sensitive to molecular surface coverage. We have measured a Δλ = 1.0 nm resonance shift when a monolayer of streptavidin protein is bound to the sensor surface, or a 60% reflectivity change when measured at a fixed wavelength.

Multimode-Interference (MMI) devices are fundamental building blocks in photonic integrated circuits, where they are used for power splitting and combining, optical switches and modulators, Mach-Zehnder interferometers and 90o hybrids for coherent optical receivers. MMIs are based on the self-image principle, by which the guided modes of the multimode region interfere to form replicas of the input field with specific amplitude and phase relations. These relations are known to depend on i) the core/cladding refractive indexes (n₁/n₂), ii) the core width (W) and length (L) of the multimode region and iii) the number, width and position of the access ports. In this work, we show that by using sub-wavelength structures within an MMI, the self-imaging properties can be significantly altered, leading to ultra-short or ultra-broadband devices., 2013 Conference on Lasers & Electro-Optics Europe & International Quantum Electronics Conference 2013, CLEO EUROPE/IQEC, May 12-16 2013, Munich, Germany

We demonstrate silicon photonic wire evanescent field sensors formed by folding long photonic wire waveguides into dense spiral paths that occupy spot sizes less than 150 mum in diameter, and are hence suitable for biochip array formats. These sensors are incorporated into both ring resonator and Mach-Zehnder interferometer (MZI) interrogation circuits, and tested by monitoring streptavidin protein adsorption. The level of detection is less than 1% of a monolayer in either configuration. Using a balanced MZI design, we show that the sensors can be insensitive to temperature and wavelength, while retaining a very high sensitivity to molecular adsorption.

Densely folded silicon wire waveguide evanescent field sensors demonstrate high sensitivity and compact foot-print. Real time monitoring of molecular binding resolves ~0.2% of a protein monolayer, corresponding to a mass of ~5 femtograms.

We demonstrate for the first time silicon chip based instantaneous chromatic dispersion monitoring of an ultra-high bandwidth 640 Gbit/s DPSK signal. This monitoring scheme is based on cross-phase modulation in an ultra-high nonlinear silicon nano-wire.

We present several new concepts to extend the capabilities of arrayed waveguide grating spectrometers. Strong lateral mode confinement wavegaide structure in the focal plane is used to increase resolution, a Michelson-type AWG spectrometer can improve optical throughput or etendue, and we show that AWG dispersion can be magnified many times by modifying the waveguide group index.

Quasi-phase matching (QPM) employs a short period modulation or grating in the second order nonlinearity, X/sup 2/, to compensate for the phase mismatch of the pump and signal beams in a second order nonlinear process. The main challenge in implementing QPM is to incorporate this X/sup 2/ grating into the waveguide. We are investigating the use of patterned ion implantation of asymmetric quantum wells (AQWs) as a means of achieving this goal.

To the Editor: The amplification of cellular proto-oncogenes, a common feature of malignant tumors, results in distinct cytogenetic alterations in carcinomas and hematopoietic neoplasms. In carcinomas, it mainly produces elongation of chromosomes by homogeneously staining regions or

We have experimentally demonstrated several InAs/InP quantum dot C-band coherence frequency comb lasers with the frequency spacing from 10 GHz to 100 GHz with the total output power of up to 50 mW. © 2013 Optical Society of America., CLEO: Science and Innovations, CLEO_SI 2013, 9 June 2013 through 14 June 2013, San Jose, CA

We demonstrate a silicon-chip-based radio-frequency spectrum analyser capable of measuring terabaud optical data. We investigate application to optical performance monitoring and show that free-carrier effects have a negligible impact on device operation.

We present a silicon-chip-based optical performance monitor, using an all-optical RF spectral analysis technique, capable of real-time performance monitoring both phase and intensity encoded signals. The device operates unimpeded by the effects of photo-generated free-carriers., OSA Topical Meeting on Photonics in Switching, July 25-28, 2010, Monterey, California

We report the first focused ion beam milled silicon-on-insulator waveguide Bragg gratings. We further demonstrate that higher order lossy modes dramatically affect the transmission spectra of surface gratings even in single-mode waveguides., IEEE International Conference on Group IV Photonics, 29 Sept.-1 Oct. 2004, Hong Kong, China

We demonstrate all-optical time division demultiplexing from 160Gb/s and 640Gb/s, down to10Gb/s in the C-band, based on four-wave mixing (FWM) in a silicon nanowire. We achieve efficient demultiplexing at both bit rates and at 160Gb/s obtain error-free operation with a system penalty of ∼ 3.9dB at 10−9 BER.

We introduce several types of new waveguide spectrometers, namely a high-resolution 50-channel AWG spectrometer, a 40-channel broadband AWG spectrometer, a Si-wire sidewall grating multiplexer, and the first planar waveguide Fourier-transform spectrometer.

Background Myc is a well known driver of lymphomagenesis, and Myc-activating chromosomal translocation is the recognized hallmark of Burkitt lymphoma, an aggressive form of non-Hodgkin's lymphoma. We developed a model that mimics this translocation event by inserting a mouse Myc cDNA gene into the immunoglobulin heavy chain locus, just upstream of the intronic Eμ enhancer. These mice, designated iMycEμ, readily develop B-cell lymphoma. To study the mechanism of Myc-induced lymphoma, we analyzed signaling pathways in lymphoblastic B-cell lymphomas (LBLs) from iMycEμ mice, and an LBL-derived cell line, iMycEμ-1. Results Nuclear factor-κB (NF-κB) and signal transducer and activator of transcription 3 (STAT3) were constitutively activated in iMycEμ mice, not only in LBLs but also in the splenic B-lymphocytes of young animals months before tumors developed. Moreover, inhibition of either transcription factor in iMycEμ-1 cells suppressed growth and caused apoptosis, and the abrogation of NF-κB activity reduced DNA binding by both STAT3 and Myc, as well as Myc expression. Inhibition of STAT3 signaling eliminated the activity of both NF-κB and Myc, and resulted in a corresponding decrease in the level of Myc. Thus, in iMycEμ-1 cells NF-κB and STAT3 are co-dependent and can both regulate Myc. Consistent with this, NF-κB and phosphorylated STAT3 were physically associated with one another. In addition, LBLs and iMycEμ-1 cells also showed constitutive AKT phosphorylation. Blocking AKT activation by inhibiting PI3K reduced iMycEμ-1 cell proliferation and caused apoptosis, via downregulation of NF-κB and STAT3 activity and a reduction of Myc levels. Co-treatment with NF-κB, STAT3 or/and PI3K inhibitors led to additive inhibition of iMycEμ-1 cell proliferation, suggesting that these signaling pathways converge. Conclusions Our findings support the notion that constitutive activation of NF-κB and STAT3 depends on upstream signaling through PI3K, and that this activation is important for cell survival and proliferation, as well as for maintaining the level of Myc. Together, these data implicate crosstalk among NF-κB, STAT3 and PI3K in the development of iMycEμ B-cell lymphomas.