1,720,961 research outputs found
High-performance ultrafast humidity sensor based on microknot resonator-assisted Mach-Zehnder for monitoring human breath
No full textMonitoring the dynamic humidity requires sensors with fast response and anti-electromagnetic interference, especially for human respiration. Here, an ultrafast fiber-optic breath sensor based on the humidity-sensitive characteristics of gelatin film is proposed and experimentally demonstrated. The sensor consists of a microknot resonator superimposed on a Mach–Zehnder (MZ) interferometer produced by a tapered single-mode fiber, which has an ultrafast response (84 ms) and recovery time (29 ms) and a large dynamic transmission range. The humidity in dynamic ambient causes changes in the refractive index of gelatin coating, which could trigger spectral intensity transients that can be explicitly distinguished between the two states. The sensing principle is analyzed using the traditional transfer-matrix analysis method. The influence of coating thickness on the sensor’s trigger threshold is further investigated. Experiments on monitoring breath patterns indicate that the proposed breath sensor has high repeatability, reliability, and validity, which enable many other potential applications such as food processing, health monitoring, and other biomedical applications
High-sensitivity humidity sensor based on microknot resonator assisted agarose-coated mach-zehnder interferometer
No full textAn optical fiber humidity sensor with a microfiber knot resonator (MKR) nested U-shaped Mach-Zehnder (MZ) interferometer based on the Vernier effect is proposed. While the reference arm is protected by cured ultraviolet glue, the sensing arm is coated by agarose. The Vernier effect is realized by superimposing the comb-like transmission spectra of the MKR and MZ interfernce, which are designed to have slightly different free spectral ranges. Experimental results indicate that the proposed sensor can provide a maximum humidity sensitivity of 2.442 nm/%RH with a measurement range from 60% RH to 95% RH. The sensor temperature response, reversibility and repeatability are also investigated. The response time is found to be 102 ms for a change of 30% RH. This sensor not only retains key features and merits of the MKR, including low cost and small footprint, but also has a simpler preparation process compared with conventional sensors based on the Vernier effect
Periodic optical filter based on high-Q nested multiple coupled-knots resonator
No full textA periodic optical filter based on nested knots resonator structure is proposed. The structure consists of a knot resonator with a number of smaller coupled-knot-resonators nested in it, similarly to a dual-bus coupled ring resonator, where the end bus terminations are connected to form a Mach–Zehnder interferometer. The variation of periodical transmission output is shown to be mainly due to the change of field components that results in constructive or destructive interference between the nested multiple coupled-knots and the outer loop. The coupling matrix formalism is used to investigate the influence of the number of coupled-knots and their coupling coefficient on the transmission spectrum. The theoretical result shows that the temperature effect can be eliminated by immersing the resonator in ethanol solution. The output spectrum from a fabricated sample with high-Q is also presented. The device is capable of generating a periodical spectral filtering response and has potential applications as a filter or interleaver
Investigation of Dy<sup>3+</sup>/Tm<sup>3+</sup> co-doped ZrF<sub>4</sub>-BaF<sub>2</sub>-YF<sub>3</sub>-AlF<sub>3</sub> fluoride glass for efficient 2.9 μm mid-infrared laser applications
No full textDifferent doping concentrations of Dy3+/Tm3+ in ZrF4-BaF2-YF3-AlF3 (ZBYA) fluoride glass samples were prepared by the melt-quenching method. Spectroscopic properties were analyzed through absorption (from 200 to 3300 nm) and emission spectra (from 1200 to 3200 nm). The spontaneous radiative transition probability, branching ratio and radiative lifetime of various energy levels transition were calculated based on the Judd-Ofelt theory. The emission cross-section value of the 1 mol% Dy3+/1 mol% Tm3+ co-doped ZBYA sample at 2.9 μm were calculated as 3.79×10-21 cm2. Near- and mid-IR emission spectra of Dy3+/Tm3+ co-doped ZBYA-fluoride glass under the excitation of 808 nm laser diode were investigated and discussed. Analysis of the emission spectra and the energy transition process of Dy3+/Tm3+ co-doped glass indicated that the introduction of Tm3+ ions can effectively improve the mid-infrared fluorescence intensity of Dy3+ ions, thus the Dy3+/Tm3+ co-doped ZBYA-fluoride glass can be an excellent candidate material for 2.9 μm mid-infrared laser applications.<br/
Tm<sup>3+</sup>-doped fluorotellurite glass microsphere resonator laser at 2.3 μm
No full textIn this Letter, we report lasing at 2.3 μm in Tm3+-single-doped and Tm3+=Ho3+-codoped fluorotellurite glass microsphere resonators. By employing a 793 nm diode laser as a pump and exploiting whispering gallery mode microresonators (WGMRs), dual-wavelength lasing at 1.9 and 2.3μm and triple-wavelength lasing at 1.9, 2.07, and 2.3μm are achieved in Tm3+-doped and Tm3+=Ho3+-codoped microspheres, respectively. The introduction of Ho3+ ions significantly reduces the lasing threshold of Tm3+ at 2.3 μm because of energy transfer.</p
Passive photonic integrated ratiometric wavelength monitor with resolution better than 15 pm
Full text linkThis paper presents a compact and low-loss photonic integrated device consistingof a Y-branch and a pair of multimode interferometers (MMI) for a ratiometric wavelength monitoring around 1550 nm on silicon-on-insulator (SOI) technique. Two MMIs are designed in terms of width and length to achieve overlapping but opposite slope spectral responses used as two edge filters over a wavelength measurement range from 1500 nm to 1600 nm. The developed integrated photonic ratiometric structure demonstrates a suitable discrimination range for a high-speed passive wavelength measurement, with a high resolution better than 15 pm over a 100 nm wavelength range
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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