Abiotic and biotic factors affecting Rhagoletis mendax [Diptera :Tephritidae] populations in eastern Canadian lowbush blueberry fields

Une étude a été effectuée en Nouvelle-Ecosse et au Nouveau-Brunswick au Canada, afin d'identifier des facteurs naturels de régulation, tels que l'acidité du sol et la présence de mauvaises herbes, qui pourraient influencer l'occurrence de populations de la mouche de l'airelle (Rhagoletis mendax) dans les bleuetières naines commerciales (Vaccinium angustifolium). Les niveaux observés d'acidité du sol n'ont pas été identifiés comme un facteur régissant la distribution et la mortalité des larves et des pupes du R. mendax. Les mouvements migratoires des adultes ont été affectés par la pratique culturale du brûlage des champs de bleuets aux deux ans et il en résulte que les adultes, émergeant de la portion brûlée des champs, migrent vers les zones en production. Une corrélation positive entre l'intensité de la pousse des mauvaises herbes indigènes et les niveaux d'infestation de la mouche de l'airelle a été démontrée.An investigation was carried out in Nova Scotia and New Brunswick, Canada, to identify natural regulatory factors, such as soil acidity and weed incidence, that could influence the occurrence of blueberry maggot (Rhagoletis mendax) populations in commercial lowbush blueberry fields (Vaccinium angustifolium). Over the range observed, the soil acidity had no detectable influence on the distribution and mortality of R. mendax larvae and pupae. Adult migrational patterns were affected by the cultural practice of burning on alternate years causing the emerging adults of burned fields to move toward sareasin production. There was also a positive correlation between the growth intensity of indigenous weeds and blueberry maggot infestation levels

Shell evolution approaching the N=20 island of inversion : Structure of 26Na

The levels in 26Na with single particle character have been observed for the first time using the d(25Na, pγ) reaction at 5 MeV/nucleon. The measured excitation energies and the deduced spectroscopic factors are in good overall agreement with (0+1)hω shell model calculations performed in a complete spsdfp basis and incorporating a reduction in the N=20 gap. Notably, the 1p3/2 neutron configuration was found to play an enhanced role in the structure of the low-lying negative parity states in 26Na, compared to the isotone 28Al. Thus, the lowering of the 1p3/2 orbital relative to the 0f7/2 occurring in the neighbouring Z=10 and 12 nuclei - 25,27Ne and 27,29Mg - is seen also to occur at Z=11 and further strengthens the constraints on the modelling of the transition into the island of inversion

Temperature-independent vertically coupled double-ring sensor

Optical biosensors on silicon platforms have demonstrated their great potential in label-free detection and analysis tool. The major challenge of ring resonator based optical biosensors is their high sensitivity to temperature variations. We have designed a double-ring resonator biosensor using a vertical coupling method. Simulation results show that the double-ring configuration effectively eliminates the temperature and environmental fluctuations by the resonant wavelength shift correction induced from the reference ring. The coupling gap in the vertical coupling method can be tuned by timing the deposition/growth rate of the space layer, without the need of any advanced lithography. The vertical coupling method allows a low fabrication cost

Review of silicon photonics: History and recent advances

Silicon photonics has attracted tremendous attention and research effort as a promising technology in optoelectronic integration for computing, communications, sensing, and solar harvesting. Mainly due to the combination of its excellent material properties and the complementary metal-oxide semiconductor (CMOS) fabrication processing technology, silicon has becoming the material choice for photonic and optoelectronic circuits with low cost, ultra-compact device footprint, and high-density integration. This review paper provides an overview on silicon photonics, by highlighting the early work from the mid-1980s on the fundamental building blocks such as silicon platforms and waveguides, and the main milestones that have been achieved so far in the field. A summary of reported work on functional elements in both passive and active devices, as well as the applications of the technology in interconnect, sensing, and solar cells, is identified

Silicon Mach-Zehnder interferometer racetrack microring for sensing

SOI-based microring resonators (MRRs) have attracted extensive attentions as ultra-compact sensors. Recently, a new structure design combining a ring and a Mach-Zehnder interferometer (MZI) was proposed as sensors for biomedical applications, and as modulators for communications applications. In this design, the MZI uses two identical couplers, where one arm is formed by connecting the access waveguide of the couplers, while the other arm is part of the microring. Such a device may have only one major resonance with a high extinction ratio in a very broad wavelength span (quasi-free spectral range, quasi-FSR), which offers a very large measurement range for sensing applications. 2×2 multimode interference (MMI) couplers are used to couple the microring and the bus waveguides as MMI couplers have broader wavelength responses. We present the first experimental demonstration of the MMI-coupled MZI racetrack microrings for sensing applications. Two types of MMI-coupled MZI racetrack microrings are discussed: one with wire waveguides, and the other using slotted waveguides. For the MZI racetrack microring using wire waveguides, we achieve a quasi-FSR of 34.3 nm near the wavelength of 1520 nm. The corresponding major resonance of the MZI racetrack microring demonstrates a high extinction ratio of ~22.4 dB with a full-width-half-maximum (FWHM) of 1.94 nm, and a quality factor Q of ~800. On the other hand, the quasi-FSR of the MZI racetrack microring with slot waveguides is 23.2 nm near the wavelength of 1540 nm; and the extinction ratio of the major resonance is ~24.5 dB with λFWHM=0.82 nm and Q=~1,900. To demonstrate the uses for sensing applications, we measure the resonance shifts corresponding to the concentration change of the ambient aqueous solutions of sucrose. DI water is used as the reference for calibration to avoid any other variations, e.g. temperature change. Experiments show that the sensitivities of the MZI racetrack microring sensors with wire and slot waveguides are 101.7 nm/RIU and 166.7 nm/RIU, respectively

Slotted silicon microring resonators with multimode interferometer couplers

We demonstrate a SOI slotted microring resonator using a multimode interferometer (MMI) coupler. We achieved high bandwidth of 0.25 nm, and a quality factor Q of ∼6000 for rings with a radius of 20 μm

Vertically coupled Si-based athermal double-ring biosensor

A silicon-based athermal double-ring resonator biosensor with a vertically coupled configuration is developed. We present an optimal design of the sensor structure by specifying the radii of the reference and the sensing rings, the vertical coupling offset, d, between the two rings and the bus waveguide, and the lateral offset, l, between the edges of the rings and the bus waveguide. By using Lumerical software package, we demonstrate that the optimal vertical and lateral offsets are d=325 nm and l=-80 nm, respectively. One major challenge faced by ring based biosensors is their temperature dependent characteristics. In this study, the sensing ring is exposed to the biomaterial under test, while the reference ring provides a temperature-insensitive reference to the sensing measurements. By assuming the biomaterial medium has small variations in temperature, we conclude that the proposed biosensor device offers temperature insensitive measurement, where the temperature effects are fully corrected by the reference ring response. The double-ring sensors are proposed to be fabricated with the local oxidation of silicon process, without the need for advanced lithography methods such as e-beam or deep UV lithography. In addition, the vertically coupled double-ring configuration allows precise control of the critical coupling separation between the rings and the bus waveguide. The proposed silicon double-ring biosensor can be used for highly sensitive and stable sensing for both biomedical and environmental applications

Silicon MMI-coupled slotted conventional and MZI racetrack microring resonators

We experimentally demonstrate two types of silicon-on-insulator microring devices: 1) a slotted conventional microring resonator (MRR) using a multimode interferometer (MMI) coupler as the coupling element; and 2) an MMI-coupled slotted Mach-Zehnder interferometer (MZI) racetrack microring. We achieved a high bandwidth of 1.1 nm and a quality factor Q of ∼ 1300 at the wavelength of 1510 nm for the conventional MRRs with a radius of 20 μ. A high extinction ratio (17-25 dB) is exhibited over a wavelength range from 1490 to 1520 nm. At the 1515-nm resonance wavelength, the MMI-coupled MZI racetrack microring demonstrates a quasi-free spectral range of 22.6 nm with a high extinction ratio of 25 dB. The demonstrated devices have many applications such as biochemical and gas sensing and modulation in communication systems

All-optical single resonance control using a silicon-based ringassisted mach-zehnder interferometer

CMOS-compatible ring-based active devices have attracted significant attention for their ability to confine and manipulate light on a compact SOI platform. Active modulation of a ring resonator is typically achieved by changing the intensity response. As an alternative to intensity modulation, the phase modulation of the ring resonator can be converted into intensity modulation of a Mach-Zehnder interferometer (MZI) by means of a ring-assisted Mach-Zehnder interferometer (RAMZI) structure. We theoretically demonstrate an all-optical single resonance switching using a silicon RAMZI by optically controlling the intracavity loss of the side-coupled silicon ring based on inverse Raman scattering (IRS). The RAMZI structure improves the modulation robustness against fabrication deviations by relaxing the coupling condition for the ring resonator, without compensating the modulation performance. In silicon, the IRS produces optical loss with a bandwidth of 105 GHz at the anti-Stokes wavelength, which blueshifts 15.6 THz from the control light. For our proposed RAMZI structure, the IRS induced loss is spectrally wider than the linewidth of the side-coupled ring, but narrower than the free spectral range (FSR) of the ring, guaranteeing single resonance selectivity. When the control light pulse of 200 ps switches from off (zero) to on (20pJ), the transmission of the anti-Stokes resonance transfers from 1.7% to 92.3%. The proposed structure provides the potential to multichannel all-optical routers on a CMOS compatible platform

Experimental demonstration of a two-mode (de)multiplexer based on a taper-etched directional coupler

We experimentally demonstrate a compact, low-cross talk and fabrication-tolerant two-mode (de)multiplexer on the silicon-on-insulator platform. The device consists of a silicon wire waveguide coupled to a taper-etched waveguide. The partially etched taper structure is used to relax fabrication tolerance and thus to ensure high mode-conversion efficiency. The device is 68 μm in length, with a TE0-to-TE1 mode conversion loss of better than -0.8 dB demonstrated over the C-band wavelengths. In addition, the device demonstrates a low TE0-to-TE0 through waveguide insertion loss of better than -1.3 dB with modal cross talk lower than -26 dB, over a 65 nm wavelength range. Finally, we have experimentally demonstrated that the device is tolerant of fabrication errors of up to 20 nm. Better than -6 dB TE0-TE1 conversion loss with a cross talk lower than -23 dB over a 55 nm bandwidth has been obtained with a fabrication tolerance as large as 40 nm