Kinetic study of hydrogen lateral diffusion at high temperature in a directly-bonded InP-SiO2/Si substrate.

Hybrid integration of III-V materials onto silicon by direct bonding technique is a mature and promising approaches to develop advanced photonic integrated devices into the silicon photonics platform. In this approach, the III-V material stack is grown on an InP wafer in a unique epitaxial step prior to the direct bonding process onto the silicon-on-insulator wafer. Currently, no additional epitaxial regrowth steps are implemented after bonding. This can be seen as a huge limitation as compared to the III-V on III-V wafer mature technology where multi-regrowth steps are most often implemented. In this work, we have studied the material behavior of an InP membrane on silicon (InPoSi) under epitaxial regrowth conditions by metal-organic vapor phase epitaxy (MOVPE). MOVPE requires high-temperature elevation, typically above 600 °C. We show for the first time the appearance of voids at 400 °C in an InP seed (100 nm) directly-bonded onto a thermally oxidized Si substrate despite the use of a thick SiO2 oxide (200 nm) at the bonding interface. This phenomenon is explained by a weakening of the bonding interface while high-pressurized hydrogen is present. A kinetic study of the hydrogen lateral diffusion is carried out, enabling the assessment of its lateral diffusion length. To overcome the void formation, highly efficient outgassing trenches after bonding are demonstrated. Finally, high-quality AlGaInAs-based multi-quantum well (MQW) heterostructure surrounded by two InP layers was grown by MOVPE on InPoSi template patterned with outgassing trenches. This process is not only compatible with MOVPE regrowth conditions (650 °C under PH3) but also with conventional fabrication processes used for photonic devices.

Directly modulated and fully tunable hybrid silicon lasers for future generation of coherent colorless ONU.

We propose and demonstrate asymmetric 10 Gbit/s upstream--100 Gbit/s downstream per wavelength colorless WDM/TDM PON using a novel hybrid-silicon chip integrating two tunable lasers. The first laser is directly modulated in burst mode for upstream transmission over up to 25 km of standard single mode fiber and error free transmission over 4 channels across the C-band is demonstrated. The second tunable laser is successfully used as local oscillator in a coherent receiver across the C-band simultaneously operating with the presence of 80 downstream co-channels.

A hybrid electroabsorption modulator device for generation of high spectral-efficiency optical modulation formats.

We report a novel hybrid integrated optic device consisting of AlGaInAs/InP electroabsorption modulators and a four-arm silica-on-silicon planar lightwave circuit optical interferometer. The device is designed for generation of high spectral efficiency optical modulation formats. We demonstrate generation of 21.4 Gb/s quadrature phase shift keyed optical signals with electrical data drives of 2V(pp) amplitudes, achieving a bit error rate of 10(-9) with the required optical signal to noise ratio of ~18 dB in a 0.1 nm resolution bandwidth.

The chemical and biological properties of methoxyfenozide, a new insecticidal ecdysteroid agonist.

Methoxyfenozide [N-tert-butyl-N'-(3-methoxy-o-toluoyl)-3,5-xylohydrazide; RH-2485] is the newest diacylhydrazine insecticide to reach the marketplace. It binds with very high affinity to the ecdysone receptor complex (EcR:USP) in lepidopteran insects [Kd = 0.5 nM (Plodia)], where it functions as a potent agonist, or mimic, of the insect molting hormone, 20-hydroxyecdysone (20E). Methoxyfenozide exhibits high insecticidal efficacy against a wide range of important caterpillar pests, including many members of the family Pyralidae, Pieridae, Tortricidae and Noctuidae. It is most effective when ingested by the target caterpillar, but it also has some topical and ovicidal properties. It is modestly root systemic, but not significantly leaf-systemic. Evidence collected to date indicates that methoxyfenozide has an excellent margin of safety to non-target organisms, including a wide range of non-target and beneficial insects.

Isolation and characterization of a novel insecticidal crystal protein gene from Bacillus thuringiensis subsp. aizawai.

Bacillus thuringiensis subsp. aizawai EG6346, a novel grain dust isolate, was analyzed by Southern blot hybridization for its insecticidal crystal protein (ICP) gene profile. Strain EG6346 lacks previously characterized cryIA ICP genes yet does possess novel cryI-related gene sequences. A recombinant genomic plasmid library was constructed for strain EG6346 in Escherichia coli. One recombinant plasmid, pEG640, isolated from the library contained a novel ICP gene on a 5.7-kb Sau3A insert. The sequence of this gene, designated cryIF, was related to, but distinct from, the published sequences for other cryI genes. A second novel cryI-related sequence was also located on pEG640, approximately 500 bp downstream from cryIF. Introduction of cryIF into a Cry- B. thuringiensis recipient strain via electroporation enabled sufficient production of CryIF protein for quantitative bioassay analyses of insecticidal specificity. The CryIF crystal protein was selectively toxic to a subset of lepidopteran insects tested, including the larvae of Ostrinia nubilalis and Spodoptera exigua.

Insecticidal toxins from Bacillus thuringiensis subsp. kenyae: gene cloning and characterization and comparison with B. thuringiensis subsp. kurstaki CryIA(c) toxins.

Genes encoding insecticidal crystal proteins were cloned from three strains of Bacillus thuringiensis subsp. kenyae and two strains of B. thuringiensis subsp. kurstaki. Characterization of the B. thuringiensis subsp. kenyae toxin genes showed that they are most closely related to cryIA(c) from B. thuringiensis subsp. kurstaki. The cloned genes were introduced into Bacillus host strains, and the spectra of insecticidal activities of each Cry protein were determined for six pest lepidopteran insects. CryIA(c) proteins from B. thuringiensis subsp. kenyae are as active as CryIA(c) proteins from B. thuringiensis subsp. kurstaki against Trichoplusia ni, Lymantria dispar, Heliothis zea, and H. virescens but are significantly less active against Plutella xylostella and, in some cases, Ostrinia nubilalis. The sequence of a cryIA(c) gene from B. thuringiensis subsp. kenyae was determined (GenBank M35524) and compared with that of cryIA(c) from B. thuringiensis subsp. kurstaki. The two genes are more than 99% identical and show seven amino acid differences among the predicted sequences of 1,177 amino acids.

Activation of a cryptic crystal protein gene of Bacillus thuringiensis subspecies kurstaki by gene fusion and determination of the crystal protein insecticidal specificity.

DNA hybridization with the insecticidal crystal protein gene cryllA (formerly cryBl) of Bacillus thuringiensis supspecies kurstaki has shown that subspecies kurstaki contains a cryllA-related sequence in addition to the cryllA gene (Donovan et al., 1988a). We have cloned the cryllA-related sequence and have determined that the sequence, which has been designated cryllB, is 89% identical to the cryllA gene. Recombinant B. thuringiensis cells harbouring the cloned cryllB gene produced very little CryllB protein. A high level of production of the CryllB protein was achieved by fusing the regulatory region of the crylllA crystal protein gene to the cryllB gene. The CryllB protein was found to be highly toxic to Lymantria dispar, Heliothis virescens and Trichoplusia ni, and was not toxic to Aedes aegypti.

Novel cloning vectors for Bacillus thuringiensis.

Seven replication origins from resident plasmids of Bacillus thuringienis subsp. kurstaki HD263 and HD73 were cloned in Escherichia coli. Three of these replication origins, originating from plasmids of 43, 44, and 60 MDa, were used to construct a set of compatible shuttle vectors that exhibit structural and segregational stability in the Cry- strain B. thuringiensis HD73-26. These shuttle vectors, pEG597, pEG853, and pEG854, were designed with rare restriction sites that permit various adaptations, including the construction of small recombinant plasmids lacking antibiotic resistance genes. The cryIA(c) and cryIIA insecticidal crystal protein genes were inserted into these vectors to demonstrate crystal protein production in B. thuringiensis. Introduction of a cloned cryIA(c) gene from strain HD263 into a B. thuringiensis subsp. aizawai strain exhibiting good insecticidal activity against Spodoptera exigua resulted in a recombinant strain with an improved spectrum of insecticidal activity. Shuttle vectors of this sort should be valuable in future genetic studies of B. thuringiensis as well as in the development of B. thuringiensis strains for use as microbial pesticides.