125,319 research outputs found
Investigation of a novel silicon-on-insulator Rib-Slot photonic sensor based on the vernier effect and operating at 3.8 µm
No full textIn this paper, we present the theoretical investigation of photonic sensors based on Vernier effect with two cascade-coupled ring resonators in silicon on insulator technology. The photonic chip utilizes rib and slot waveguides designed to operate at 3.8 µm mid infrared wavelength, where a number of harmful gases, chemical and biochemical analytes are spectroscopically accessible. A rigorous algorithmic procedure has been implemented for the design of such devices and novel technological solutions have been proposed according to very recent experimental results. The rib-slot sensor architecture can exhibit wavelength sensitivities as high as 20.6 µm/RIU and limits of detection for homogeneous sensing as low as 3.675 × 10−4 RIU
A generalized approach for design of photonic gas sensors based on Vernier effect in mid-IR
No full textIn this paper a generalized approach for modeling and design of photonic sensors based on Vernier effect
is presented. Design criteria of integrated optical architectures based on multiple ring resonators are
found, customized as a function of a specific gas to be monitored. Very efficient performance has been
demonstrated in mid-IR operative wavelength range. Sensitivities of the order of 105 nm/RIU and limits of detection as low as 10^−5 RIU allow detecting very small traces of methane and ethane in air
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Cascaded ring resonator and Mach-Zehnder interferometer with a Sagnac loop for Vernier-effect refractive index sensing
No full texttIn this paper, we propose a novel photonic integrated sensor characterized by the cascade of a ringresonator (RR) and a Mach-Zehnder interferometer (MZI) architecture with a Sagnac loop (i.e., RR-MZI-Sagnac). We present the modelling and detailed guidelines for the design of such devices that are assumedto be fabricated on complementary metal-oxide semiconductor (CMOS) compatible silicon-on-insulator(SOI) platforms. Ultra-high refractive index (RI) sensing performance such as wavelength sensitivitieslarger than 2.5 × 103m/RIU (RI unit) and limits of detection (LOD) of 1 × 10−8RIU can be achieved byemploying the Vernier effect in the near-infrared (NIR), around the wavelength of 1.55 m. Furthermore,we theoretically demonstrate that the novel RR-MZI-Sagnac Vernier devices can operate better than themost performing state-of-the-art Vernier sensors characterized by cascaded RR and MZI (RR-MZI). Infact, an operating bandwidth that is half than that requested by the RR-MZI devices is exhibited whenbalanced MZIs are designed in both configurations, still preserving similar RI sensing performance. Alter-natively, double RI sensing performance can be achieved by RR-MZI-Sagnac Vernier sensors with respectto RR-MZI devices when unbalanced MZIs are considered in both the Vernier configurations, exhibitingthe same operating bandwidths. Finally, simulations reveal that ammonia (NH3) concentrations in the0–30,000 ppm range and carbon dioxide (CO2) traces lower than 5,000 ppm can be detected in deionizedwater and air, respectively
Group IV Materials for High Performance Methane Sensing in Novel Slot Optical Waveguides at 2.883 μm and 3.39 μm
No full textIn this paper a detailed investigation of novel photonic sensors based on slot waveguides has been carried out. Appropriate alloys of group IV materials, such as germanium (Ge), silicon (Si), carbon (C) and tin (Sn), are applied in silicon-on-insulator (SOI) technology for homogeneous optical sensing at 2.883 μm and 3.39 μm. Electronic and optical properties of group IV alloys have been investigated. In addition, we have designed novel group IV vertical slot waveguides in order to achieve ultra-high sensitivities, as well as good fabrication tolerances. All these features have been compared with well-known SOI slot waveguides for optical label-free homogeneous sensing at 1.55 μm. In conclusion, theoretical investigation of ring resonators based on these novel slot waveguides has revealed very good results in terms of ultra high sensing performance of methane gas, i.e., limit of detection ~ 3.6×10-5 RIU and wavelength sensitivity > 2×103 nm/RIU
Generalized modelling for the design of guided-wave optical directional couplers
No full textIn this Letter we propose a rigorous and generalized approach for the design of integrated optical bent directional couplers (DCs) based on the coupled mode theory and super mode theory. The full vectorial finite-element method is used for the calculation of effective indices of optical modes propagating into the waveguides constituting the DCs. The flexibility and robustness of this general modelling approach is demonstrated by simulating several directional coupling configurations, as those based on cosine S-bend and double arc bent waveguides. Furthermore, some numerical results have been validated by comparison with the three-dimensional semi-vectorial beam propagation method
Mid-IR Optical and Non Linear Properties of Germanium on Silicon Optical Waveguides
No full textThe influence of Germanium-on-Silicon waveguide geometries on single-mode and multimode operations as well as on zero birefringence conditions has been deeply investigated in the mid infrared spectrum. The design equations to estimate the single mode conditions have been carried out and interpolated by exponential functions. Moreover, the group velocity dispersion and third-order dispersion have been investigated in the range 3-6 mu m as a function of various waveguide geometries. Finally, nonlinear properties, for instance the modal Raman gain, have been investigated, comparing with Silicon-on-Insulator waveguides. The set of results identifies accurate guidelines for the design of these optical waveguides for several applications
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