111 research outputs found

    Comparison between Vernier-cascade and MZI as transducer for biosensing with on-chip spectral filter

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    The Mach-Zehnder interferometer (MZI) and the Vernier-cascade are highly responsive photonic sensors with large design freedom. They are therefore very suitable for interrogation through a broadband source and an on-chip spectral filter, a sensing scheme that is well equipped for point-of-care applications. In this work, the MZI is shown to outperform the Vernier-cascade through a better minimum detectable wavelength shift as well as a higher power efficiency, indicating its superiority in this sensing scheme. Fabricated MZIs yield bulk detection limits down to 8.8 x 10(-7) refractive index units (RIU) in a point-of-care compatible measuring setup, indicating the potential of the proposed sensing scheme

    Study on the limit of detection in MZI-based biosensor systems

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    Mach-Zehnder interferometers are integrated photonic sensors that have yielded excellent detection limits down to 10(-7) RIU. They are of particular interest due to their large design freedom, allowing for example application in promising point-of-care compatible read-out schemes. The attainable detection limit of such sensors can interact with the sensor design in different ways, depending on the dominant origin of noise which can either be influencing a single sensor arm, both sensor arms or can be unrelated to the sensor itself. In this work, the interaction of these three noise regimes with the sensor design is examined. The regimes are combined into a framework that predicts the limit of detection as a function of sensor design. A set of experimental results confirms the validity of this obtained theoretical framework. This analysis provides a blueprint for optimization of MZI photonic sensors under any combination of read-out method and measurement circumstances

    Compact silicon nitride arrayed waveguide gratings for very near-infrared wavelengths

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    In this letter, we report a novel high-index-contrast silicon nitride arrayed waveguide grating (AWG) for very near-infrared wavelengths. This device is fabricated through a process compatible with a complementary metal-oxide-semiconductor fabrication line and is therefore suitable for mass fabrication. The large phase errors that usually accompany high-index-platform AWGs are partly mitigated through design and fabrication adaptions, in particular the implementation of a two-level etch scheme. Multiple devices are reported, among which a 0.3-mm(2) device which, after the subtraction of waveguides loss, has a -1.2 dB on-chip insertion loss at the peak of the central channel and 20-dB crosstalk for operation similar to 900 nm with a channel spacing of 2 nm. These AWGs pave the way for numerous large-scale on-chip applications pertaining to spectroscopy and sensing

    Silicon photonics biosensing: different packaging platforms and applications

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    We present two different platforms integrating silicon photonic biosensors. One is based on integration with reaction tubes to be compatible with traditional lab approaches. The other uses through-chip fluidics in order to achieve better mixing of the analyte

    Label-free real-time optical monitoring of DNA hybridization using SiN Mach‚ÄďZehnder interferometer-based integrated biosensing platform

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    We report on the label-free real-time optical monitoring of DNA hybridization upon exposure to a flow of complementary DNA at different concentrations. The biosensor is composed of a silicon nitride integrated unbalanced Mach-Zehnder interferometer (MZI), with an integrated arrayed waveguide grating as a spectral filter. This MZI has been shown to have both sufficient multiplexing capability and limit of detection on the order of 10(-6) RIU. Probe DNA, consisting of a 36-mer fragment is covalently immobilized on the silicon nitride integrated biosensor. The wavelength shift is monitored upon complementary DNA targets being flown over the sensor. Concentrations of 1 pM can be easily detected. Also, an alternative route to modify the sensor surface with carboxylic groups using the photochemical reaction of fatty acids is proposed and preliminary XPS results are presented. Moreover, preliminary results for DNA obtained from a rolling circle amplification (RCA-DNA) process and spiked in a realistic amplification buffer are presented. (C) 2018 Society of Photo-Optical Instrumentation Engineers (SPIE

    Performance analysis of WiMAX for mobile applications

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    The goal of this paper is to investigate the performance of a mobile WiMAX system for various settings of its physical-layer parameters and for realistic propagation channels. For this, a physical layer model of IEEE 802.16e is developed in software. Different propagation channels are implemented, such as the Rayleigh channel and the SUI channel models. Moreover, a tapped delay line channel model is developed for a specific area in Ghent (Belgium) using raytracing software. For this area, the maximum achievable range of a realistic mobile WiMAX system is found to be 2.7 km. Additionally, the performance gain of MIMO systems with diversity is investigated. The diversity gain of a 2x2 MIMO Alamouti diversity scheme is found to vary between 3 and 5.5 dB

    Spectroscopic sensing and applications in Silicon Photonics

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    We report on miniaturized spectroscopic sensors that are realized using Silicon Photonics technology. This technology relies on CMOS compatible processes to fabricate both Silicon and Silicon-Nitride based photonics integrated circuits. Various spectroscopic sensor designs and applications are discussed
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