Optical sensors of fluid concentration based on evanescent fleld

Optički senzori su deo mnogobrojnih sistema u industriji, transportu, telekomunikacijama, medicini i nauci. Koriste se za merenje temperature, pritiska, istezanja, indeksa prelamanja okolne sredine i indirektno za merenje koncentracije gasova i tečnosti, vlažnosti i drugog. Uglavnom zahvaljujući naglom razvoju optičkih telekomunikacionih tehnologija, razvoj optičkih senzora pratio je opšti trend smanjivanja i integracija ka malim, robusnim i prenosivim urađajima. Pri tom su se izdvojila dva osnovna tipa senzora: senzori na bazi optičkih vlakana i integrisani senzori, koji su dalje funkcionalizovani hemijskim putem i korišćenjem nanotehnologija. Razvoj metoda za proizvodnju minijaturnih senzora i tankih filmova koji se nanose na površinu senzora je značajno uticao na razvoj optičkih senzora. U distertaciji su istraživani senzori na bazi integrisanih svetlosnih talasovoda funkcionalizovani tankim poroznim filmom. Princip detekcije je interakcija merene tečnosti ili gasa sa evanescentnim elektromagnetim poljem. Kod gasova je dominantna rezonantna apsorpcija svetlosti, a kod tečnosti promena profila i propagacione konstante moda usled promena indeksa prelamanja tečnosti. U oba slučaja poroznost filma omogućava veće preklapanje polja moda sa fluidom koji se meri i time osetljivost senzora. Ova teza se bavi proučavanjem uticaja parametara tankog filma na performanse senzora, osetljivost i opseg, kao i optimizacijom geometrije senzora u cilju dobijanja najviše osetljivosti. Pritom su korišćeni parametri tankih filmova i njihove varijacije određeni eksperimentalno. Rezultat rada su predlozi i dizajn ovih tipova optičkih senzora pogodnih karakteristika za određivanje koncentracije fluida upotrebom poznatih nanotehnologija. Pokazano je da se najbolja osetljivost senzora gasa javlja u slučaju talasovodnih struktura koje podržavaju modove pretežno lokalizovane u oblasti tankog poroznog filma. Takođe je pokazano da se korišćenjem poroznih filmova osetvljivost senzora povećava 20 puta u odnosu na neporozne, kao i da male varijacije debljine i poroznosti filma od 1% značajno smanjuju osetljivost senzora. Proračuni su izvedeni za senzor ugljen-dioksida u bliskom infra-crvenom opsegu...Optical sensors are nowadays present in many industrial systems, transport, telecommunication, medicine and science. These are used for measurements of temperature, pressure, refractive index of surrounding and implicitly concentration of gasses and liquids, humidity etc. Mostly due to development of telecommunication systems, optical sensors were following the trend of size decrease and integration to small, robust and transferable devices. Two types of sensor are most significant in this sense: optical fibre sensors and integrated sensors. These can be further functionalized with nanotechnology. An important influence to the development of the optical sensors is in establishing new methods of miniature sensor preparation together with methods of thin films deposition. The sensors based on integrated light waveguides with thin porous films are investigated in this dissertation. The detection principle is based on interaction of liquids and gases with evanescent electromagnetic field. Interaction of resonant light absorption is dominant in the case of gases, while the change of the mode profile and propagation constant due to change of liquid refractive index is dominant for liquids. In both cases the film porosity enables better overlapping of the mode field with the measurand which brings higher sensor sensitivity. Influence of thin film parameters on sensor performances, sensitivity and range, as well as optimization of sensor geometry with the goal to obtain the best sensitivity are the topics of investigation presented in this dissertation. Used film parameters and their variations are experimentally determined. The outcome of the investigation is the proposed design of the optical sensors for determination of fluid concentration based on usage of known nanotechnologies. It has been shown that the best gas sensor sensitivity is obtained in the case of waveguiding structures which support modes picked in the thin film area. Also, it is shown that usage of porous films increases the sensor sensitivity 20 times with respect to nonporous films and that the small variation of the film thickness (1nm) and porosity (1.5%) significantly decreased the sensor sensitivity. Calculations are conducted for CO2 in near infrared spectrum..

Monitoring of respiratory volumes by an long period grating sensor of bending

Here, we present a method of respiratory volumes monitoring using a single fiber-grating sensor of bending. Measurements are conducted using simple monochromatic interrogation scheme that relies on a photodiode measurement of the power transmitted through a long period grating (LPG) sensor at fixed wavelength. Good sensor accuracy in measurements of tidal and minute respiratory volumes for different types of breathing is achieved.Conference on Light in Nanoscience and Nanotechnology (LNN), Oct 20-22, 2015, Hissar, Bulgari

Estimation of the Sensitivity of a Multi-Parameter Fiber Grating Sensor

In this paper, we use a powerful mathematical concept based on Fisher information (FI) to estimate the cross-sensitivity of multi-parameter sensors. FI has been used in various branches of natural and social sciences [1], in both classical and quantum systems [2]. Lately, it has been used for estimation of interferometer sensitivity in quantum optics [3], as well as in classical optical interferometers [4]. Here, we expand its application to fibre grating sensors that are sensitive to several environmental (temperature, humidity) and mechanical (strain, pressure, curvature) parameters simultaneously [5]. FI is a local probability measure of obtaining an unknown parameter θ from the data measured at the sensor output, X. In the theory of measurement, FI directly enters the relation which determines the lower bound of the measurement uncertainty known as Cramer-Rao bound (CRB = 1/ FI (θ ) ). The sensor sensitivity is optimized by maximization of the corresponding FI. In the case of a multi-parameter sensor, FI assumes a matrix form defined via the probability distribution function f(X| θ) of the measured variable X conditioned by θ, where both X and θ are vector quantities. ( ) ( ) i n j n f X FI E i j i j ; 1,2,... ; 1,2,..., 2 ln , = = ∂ ∂ ∂ = − θ θ θ θ . Here, we develop a comprehensive model of the spectral response of fibre gratings to changes in multiple parameters and apply Fisher's formalism to optimize their sensitivity in the realistic parameter space. We start from a 1-parameter model of a long-period grating sensor of curvature and corroborate our approach by comparison with the conventional sensitivity models and the experimental data. We then expand the model to describe a 2-parameter long-period grating sensor of curvature and temperature. Based on this analysis, we recommend the multi-parameter interrogation scheme (estimator) and optimize grating parameters to render the highest sensitivity.V International School and Conference on Photonics and COST actions: MP1204, BM1205 and MP1205 and the Second international workshop "Control of light and matter waves propagation and localization in photonic lattices" : PHOTONICA2015 : book of abstracts; August 24-28, 2015; Belgrad

Distinct cytotoxic mechanisms of pristine versus hydroxylated fullerene

The mechanisms underlying the cytotoxic action of pure fullerene suspension (nano-C-60) and water-soluble polyhydroxylated fullerene [C-60(OH)(n)] were investigated. Crystal violet assay for cell viability demonstrated that nano-C-60 was at least three orders of magnitude more toxic than C-60(OH)(n) to mouse L929 fibrosarcoma, rat C6 glioma, and U251 human glioma cell lines. Flow cytometry analysis of cells stained with propidium iodide (PI), PI/annexin V-fluorescein isothiocyanate, or the redox-sensitive dye dihydrorhodamine revealed that nano-C-60 caused rapid (observable after few hours), reactive oxygen species (ROS)-associated necrosis characterized by cell membrane damage without DNA fragmentation. In contrast, C-60(OH)(n) caused delayed, ROS-independent cell death with characteristics of apoptosis, including DNA fragmentation and loss of cell membrane asymmetry in the absence of increased permeability. Accordingly, the antioxidant N-acetylcysteine protected the cell lines from nano-C-60 toxicity, but not C-60(OH)(n) toxicity, while the pan-caspase inhibitor z-VAD-fmk blocked C-60(OH)(n)-induced apoptosis, but not nano-C-60-mediated necrosis. Finally, C-60(OH)(n) antagonized, while nano-C-60 synergized with, the cytotoxic action of oxidative stress-inducing agents hydrogen peroxide and peroxynitrite donor 3-morpholinosydnonimine. Therefore, unlike polyhydroxylated C-60 that exerts mainly antioxidant/cytoprotective and only mild ROS-independent pro-apoptotic activity, pure crystalline C-60 seems to be endowed with strong pro-oxidant capacity responsible for the rapid necrotic cell death

Multimode Sensor of Fluids Based on Porous Film

Multimode interferometers are coming of ageboth as sensors and components of quantum circuits. Herewe investigate an interferometer based on a porous thin-film sensor of refractive index of fluids. Eigenmode anal-ysis is used to identify effective single- and multi-modesensing regimes and the corresponding realizations of in-terferometer. A general measure in a form of Fisher infor-mation is introduced to describe the impact of the filmporosity on sensitivity and nonlinearity of the interferom-eter. As high sensitivity relies on formation of a highlypeaked mode in the film, a parallel with plasmonic sen-sors is drawn. Close correlations between the sensor non-linearity, mode profile and the shape of Fisher informationfunction indicate the potential of this measure in describ-ing complex non-Gaussian multimode structures

Theoretical analysis of a Mach-Zehnder interferometer with a porous-film waveguide

Here we present a comprehensive theoretical study of a porous-film sensor of fluid in Mach-Zehnder configuration. It is found that the penetration of a fluid into the film pores causes amplitude and phase modulation of the interferometer output signal, maximizing the sensitivity at a certain value of the fluid refractive index. We define the Fisher information for this interferometer and show that it is a good measure of its sensitivity, hence suitable as an evaluation function in sensor optimization. We propose the sensor structure and design thin films that maximize its sensitivity to water, alcohol solutions and oils. The estimated sensitivity of the order of 10(-5) RIU to the fluid refractive index and of 5 pm to the changes in the film thickness indicate the potential of this sensor for applications in biomedicine, chemistry and environmental protection, and as a tool for the film characterization

Evanescent-wave optical gas sensor with a porous thin-film coating

In this paper, we present the analysis and numerical model of absorptive gas detection by an optical evanescent-wave sensor. We investigate the influence of sensor geometry and thin-film porosity on the attenuation of guided modes caused by their interaction with the gas. We show that film porosity is a critical parameter that should be carefully optimized for a chosen mode. These findings served as a basis for the design of an experimentally realizable sensor of carbon dioxide.4th International School and Conference on Photonics, Aug 26-30, 2013, Belgrade, Serbi

Modulation Instability of Two-Dimensional Dipolar Bose-Einstein Condensate in a Deep Optical Lattice

We study the stability of the continuous waves in the pancake shaped dipolar Bose-Einstein condensate trapped in the strong optical lattice potential with the coexisting local (the short-range s-wave) interaction and nonlocal (the dipole-dipole) interactions between the condensate atoms. The system is modeled by two two-dimensional discrete models derived from the Gross-Pitaevskii equation accounting the dipole-dipole interactions: discrete nonlinear Schrodinger equation with cubic nonlinearity and nonpolynomial Schrodinger equation. The corresponding dispersion relations are calculated analytically and the regions of the modulation instability in the parametric space are summarized into the stability diagrams.International School and Conference on Photonics (PHOTONICA09), Aug 24-28, 2009, Belgrade, Serbi

Bioremedijacija zagađenih zemljišta i voda

Industry, mining and agriculture produce large amount of wastes as by-products, such as heavy metals, pesticides and other organic compounds and fertilizers who's caused seriously environment pollution both in water and soils. At polluted area, many pollutants become available to local vegetation, so crop cultivation in such areas has been found to pose a hazard to human and livestock nourishment. However, certain pollutant-tolerant wild plants are characterized by a pronounced ability to uptake large amounts of different pollutants over their vegetation and reproduction period. Such plants manage to survive on contaminated soils and they have been termed metal super-accumulators. Since 1980, plant species of this type have been at the focus owing to their ability to clean up different pollutants from soil. These plants at the other hand favorite diversity, activity and multiply of different soil microorganisms (MO) which they have very important role in soil remediation. Plant roots excrete different substances (amino acids sugars and etc) that's MO used for food and such symbiotic connection enhanced remediation potential. Unlike the rather costly conventional soil remediation methods, these new technologies (phytoremediation) and MO and its combination are relatively cheap and environmentally friendly, especially for impoverished countries. About 400 wild plants species with such properties have been investigated worldwide and more than 200 different MO were patented specially for remediation of metals and organic pollutants in soils. The aims of this article are to give more details about wild and cultivars species and MO, its mechanisms for uptake and biological degradation of different pollutants and possible practical application to cleaning up the polluted soils.Veliki lignitski baseni u našoj zemlji su energetski potencijal strategijskog značaja. Razvoj površinskih kopova kao energetsko-industrijskog kompleksa prate brojni negativni uticaji na životnu sredinu, što obavezuje na integralno planiranje, revitalizaciju i uređenje degradiranih prostora i njihovo svestrano korišćenje u posteksploatacionom periodu. Rekultivacija i restrukturiranje mase otkrivke nude brojne mogućnosti. Da bi se izbegle štetne posledice razvoja površinskih kopova, termoelektrana i pogona za preradu uglja, rudarske aktivnosti treba da prati biološka rekultivacija odlagališta jalovine i uređenje degradiranih predela u cilju uspostavljanja različitih vegetacijskih i drugih ekosistema na novoformiranim deposolima. Brojna istraživanja su pokazala da je na ovako degradiranim područjima moguće stvoriti nove poljoprivredne, šumske, akvatične, livadske i druge ekosisteme. Rekultivacija je kompleks rudarsko-tehnoloških, inženjerskih, poljoprivrednih i šumsko-uzgojnih postupaka koji se preduzimaju u cilju transformacije industrijski degradiranog zemljišta u stanje pogodno za poljoprivredu i šumarstvo, rekreaciju, ribarstvo, izgradnju objekata različite namene i druge ciljeve. Generalno posmatrajući, rekultivacija podrazumeva ponovno uspostavljanje biljnih zajednica u područjima degradiranih eksploatacijom uglja, može se obavljati periodično ili u kontinuitetu, paralelno sa rudarskim aktivnostima. Nije neophodno, a često nije ni moguće restaurisati prvobitne predele i ekosisteme koji su postojali pre eksploatacije uglja. Mogu se podržati sve forme korišćenja zemljišta. Važno je da odabrani način korišćenja zemljišta zadovoljava potrebe lokalne zajednice, uslova sredine kao i osobina novoformiranih zemljišta, posteksploatacione stratigrafije i ekonomskog aspekta. Područje Kolubarsko-Tamnavskog lignitskog basena karakterišu impresivni radovi na revitalizaciji i uređenju degradiranih prostora. Do 1997. godine rekultivisano je preko 1,000 hektara. Šume se nalaze na 74.7% ukupno rekultivisane površine, poljoprivredne površine na 23%, voćnjaci na 1.3% i rasadnici na 1%. Ovakav inicijalni udeo različitih ekosistema je poželjan s obzirom da su šumski ekosistemi najznačajniji za zaštitu životne sredine. Mnogo veći udeo poljoprivrednih ekosistema se planira u daljem toku procesa eksploatacije uglja i biološke rekultivacije. U zavisnosti od mikro-ekoloških uslova i tipa deposola, korišćene su brojne četinarske i listopadne vrste drveća u postupku biološke rekultivacije pošumljavanjem. Najveću površinu zauzimaju čiste sastojine crnog i belog bora (27.2%), kao i grupe mešovitih lišćara i četinara (23.2%). Mešovite sastojine četinara učestvuju sa 11.1% u ukupno pošumljenoj površini, a mešovite sastojine lišćara sa oko 9.6%. Ostali lišćari - joha, sibirski brest, lipa i drugi učestvuju sa 7.9%, bagrem sa 8.4%, dok sve druge vrste učestvuju od 1.3% do 3.4%. Korišćen je relativno veliki broj vrsta dendroflore, ne samo zbog velike varijabilnosti mikro-ekoloških uslova što je posledica neselektivnog odlaganja otkrivke, već i u težnji da se obogati biodiverzitet i oplemene predeli u estetskom smislu. Sve korišćene vrste imaju visok stepen preživljavanja po sadnji, veoma dobru dinamiku visinskog, debljinskog i zapreminskog prirasta, ali postoje razlike između vrsta na identičnom tipu deposola, kao i razlike u razvoju svake pojedinačne vrste na različitim deposolima. Monitoring razvoja zasađene dendroflore omogućava da se za svaki tip deposola napravi optimalan izbor vrsta za pošumljavanje, kako bi se postigli najveći razvojno-produkcioni efekti, vitalnost, dekorativnost i ostale funkcionalne vrednosti. U radu su prezentirani rezultati istraživanja razvoja tri vrste roda Pinus: P. sylvestris L., P. nigra Arn. i P. strobus L