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1
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Long Period Waveguide Gratings in Planar Gradient Waveguides

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Kotyczka T., Rogoziński R.
Acta Physica Polonica A
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2012
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vol. 122
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issue 5
841-846
EN
This paper introduces the application possibilities of long-period waveguide gratings in planar structures of gradient waveguides. The analysis of resonance possibilities of coupling modes in gradient-gradient structures was carried out. An original configuration of single-mode (gradient) structure and multimode decoupling area was proposed. The refractive properties of gradient areas were calculated on the basis of experimental data relating to the Ag^{+} ↔ Na^{+} ion exchange in soda-lime glass. The calculations of the resonance properties included the actual dispersion of the glass substrate. The influence of the ion exchange technological processes (diffusion, heating) on the character of the coupling modes' curves was also presented. The calculations indicate the possibility of obtaining these resonances in the wavelength range corresponding to the visible spectrum.
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Silicon Nitride Overlays Deposited on Optical Fibers with RF PECVD Method for Sensing Applications: Overlay Uniformity Aspects

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Michalak B., Koba M., Śmietana M.
Acta Physica Polonica A
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2015
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vol. 127
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issue 6
1587-1591
EN
This work discusses uniformity of overlays deposited with radio frequency plasma enhanced chemical vapor deposition method on a core of partly uncoated multimode polymer-clad silica optical fiber. Although the method provides uniform films on flat surfaces, uniformity of deposition on optical fibers suspended in plasma is questionable. In this work we investigate optical-fiber-based structures coated with high-refractive-index (n_{D}> 2.3) silicon nitride (SiN_{x}) where lossy mode resonance phenomenon appears. Experimental studies, where the fiber is rotated by 90° and 180°, are compared to those where the sample has not been rotated between the depositions. Deposition process time for all samples has been adjusted in order to obtain the same thickness of overlays on all the fibers. The experimental data has been supported by numerical simulations. The experiment has shown that the rotation modifies transmission of the SiN_{x}-coated fiber structure, as well as its response to external refractive index. As an effect of rotation we observed shift of the resonance appearing at about λ =600 nm towards shorter wavelengths and reduction in amount of the resonances. However, the resonances appearing in transmission spectrum for sample with no rotation show the highest refractive index sensitivity reaching about 690 nm per refractive index unit.
3
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Absorption Studies on Some Silicate and Cabal Glasses Containing NiO or Fe_{2}O_{3} or Mixed NiOi + Fe_{2}O_{3}

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Moustaffa F., El-Batal F., Fayadd A., El-Kashef I.
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issue 3
471-477
EN
Ultraviolet and visible absorption of some sodium and potassium silicate and cabal glasses containing nickel oxide, ferric oxide or both nickel and ferric oxides together have been investigated. In alkali silicate glasses, nickel ions reveal no ultraviolet absorption bands but they show characteristic visible absorption bands due to octahedral and tetrahedral coordinations while iron ions show weak visible absorption bands which are related to ferric ions mostly in tetrahedral state, especially at high alkali oxide content; also iron ions reveal charge transfer ultraviolet absorption bands which are assigned mostly to ferric ions with few ferrous contributions. The proportion of tetrahedral state increases with the increase in the alkali oxide content for the two transition metal oxides. In cabal glasses, nickel ions tend to exist mostly in octahedral state, while ferric ions exist mostly in octahedral and some in tetrahedral form, all the absorption obtained are attributed to their respective energy levels. The ratio of the different coordinations states are discussed in relation to the glass composition.
4
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Preparation and Characterization of Basic and Er^{3+}-Doped Glasses in the System Y_{2}O_{3}-Al_{2}O_{3}-ZrO_{2}

100%
Klement R., Hruška B., Hronský V., Olčák D.
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vol. 126
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issue 1
302-303
EN
The undoped, and Er-doped yttrium aluminozirconate (AYZ) glasses were prepared by flame synthesis in the form of transparent glass microbeads. The ZrO_{2} content was in the range between 5 and 20 mol. %. The prepared glass microbeads were characterised by optical microscopy, SEM, XRD, DSC, ^{27}Al MAS NMR, UV-VIS-NIR and fluorescence spectroscopy. The thermal stability of AYZ glasses, expressed in terms of the difference between the glass transition temperature, T_{g}, and the onset of crystallization, T_{x}, was not affected by the increasing ZrO_{2} content. The ^{27}Al MAS NMR spectra of studied glass samples reveal that Al atoms are predominantly 4-coordinated in glasses. The AYZ5 and AYZ10 basic glasses were doped with Er^{3+} at the level of 1-5 mol. % of Er_{2}O_{3}. The UV-VIS-NIR/fluorescence spectra show characteristic absorptions/emissions, due to the optically active Er^{3+} ions in the host glasses. The absorption/emission properties of guest ions are not significantly affected by the glass host.
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Influence of Rare Earth Ions on the Optical Properties of Tellurite Glass

100%
Burtan B., Reben M., Cisowski J., Wasylak J., Nosidlak N., Jaglarz J., Jarząbek B.
Acta Physica Polonica A
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2011
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vol. 120
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issue 4
579-581
EN
The goal of this work was to investigate the influence of rare-earth ions such as Nd^{3+} and Er^{3+} on the optical properties of tellurite glass of the TeO_2-WO_3-PbO-La_2O_3 system. The optical studies of the glasses comprised spectrophotometry (reflectance and transmittance) and spectroscopic ellipsometry. The spectrophotometric measurements yield a number of narrow absorption bands which correspond to characteristic transitions between the ground- and consecutive excited states of rare-earth ions. From ellipsometric studies, in turn, the dispersion of the refraction coefficient has been obtained which appears to be practically the same for the tellurite glass matrix and the matrix doped with Nd^{3+} and Er^{3+} ions.
6
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Sol-Gel Derived Sensitive Films for Ammonia Sensors

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Tyszkiewicz C., Karasiński P., Rogoziński R.
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issue 6
1262-1266
EN
The sol-gel technology allows the preparation of silica thin films ranging in porosity from dense to highly porous films (50%). Porous silica films can function as a matrix that is able to bind the molecules of pH-sensitive indicators and therefore can be utilized as a sensitive film in construction of intensity based fibre or planar optical sensors for ammonia detection. We report the fabrication and characterization of ammonia sensitive, highly porous silica films deposited on soda-lime glass plates and doped with the bromocresole purple, and bromothymol blue molecules. In this paper we present the influence of the substrate withdrawal speed from sol on a thickness and a refractive index of the undoped silica films, as well as spectral absorbance characteristics of the doped films. An influence of ammonia concentration in air and relative humidity on a transmission of produced sensitive films is also presented.
7
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Influence of the Heating Processes on the Modal Attenuation Distribution in Planar Gradient Waveguides

100%
Kotyczka T., Rogoziński R.
Acta Physica Polonica A
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2011
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vol. 120
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issue 4
671-677
EN
In this paper the influence of the heating processes on modal attenuation distribution in planar gradient waveguides produced by ion exchange method in soda-lime glass-Ag^{+} admixture arrangement is presented. The influence of heating processes on modal attenuation distribution in dependence on preliminary refractive profile shape was analysed. Numerical simulations were based on experimentally gained thermal diffusion coefficients of the exchanged ions.
8
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Intrinsic Luminescence of the Undoped Glasses of (CaO-Ga_{2}O_{3}-GeO_{2}) System

100%
Padlyak B., Bordun O., Buchynskii P.
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vol. 95
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issue 6
921-929
EN
For the first time the intrinsic luminescence in the undoped (CaO-Ga_{2}O_{3}-GeO_{2}) glasses with different composition has been found and investigated in the 80÷300 K temperature range. The new glasses of high chemical purity and optical quality with stoichiometric composition similar to that in calcium-gallium- germanium garnet (Ca_{3}Ga_{2}Ge_{3}O_{12}), trigonal Ca-gallogermanate (Ca_{3}Ga_{2}Ge_{4}O_{14}), and Ca_{3}Ga_{2}O_{6} crystals were obtained by the high-temperature synthesis method. The luminescence and photoexcitation spectra analysis, supported by EPR spectroscopy data, yields the following results: (i) the UV-excited non-elementary broad emission band with maxima at roughly 500 nm and 420 nm in the (CaO-Ga_{2}O_{3}-GeO_{2}) glasses is due to recombination of ensemble of the transient hole O^{-} centres; (ii) the emission bands with maxima at nearly 380 and 710 nm, which were distinctly revealed in glasses with the Ca_{3}Ga_{2}Ge_{4}O_{14} and Ca_{3}Ga_{2}O_{6} compositions, are assigned to the luminescence of UV-induced electron centres of two different types. Possible models of the luminescence centres in (CaO-Ga_{2}O_{3}-GeO_{2}) glass network are discussed.
9
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Investigation of Infrared and Raman Spectra of TeO_2-Nb_2O_5-TiO_2 Glasses

100%
Kabalci İ., Gökçe H.
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vol. 125
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issue 4
877-881
EN
X-ray diffraction, infrared (IR), Raman spectroscopy and scanning electron microscope techniques have been used to investigate the microstructural properties of the glass materials. In this work, a new type of tellurite based optical glasses with TeO_2/Nb_2O_5/TiO_2 for different xNb_2O_5 (x = 5, 10, 15, and 20 mol.%) glass compositions at constant 5 mol.% TiO_2 ratio were prepared. The effect of Nb_2O_5 contents on the structural unit of (95-x)TeO_2-(x)Nb_2O_5-5TiO_2 glass network, and the intensity ratios of the Raman peaks were investigated. The results indicate that for different Nb_2O_5 content 5 to 20 mol.% in the glass system, three vibrational peaks around 650, 800, and 920 cm^{-1} which correspond to the structural bonding of the glass were observed in the range of 500-2000 cm^{-1} for the IR spectra. Furthermore, from the Raman results a structural evolution was determined with the number of structural units such as [NbO_6]^{7-}, TeO_{3+1} (polyhedra), TeO_4 (trigonal bipyramids), TeO_3 (trigonal pyramids) or TeO_{3+1} (polyhedra), and [NbO_4]^{3-} for this ternary glass system.
10
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Sensitive Films for Optical Detection of Ammonia and Nitrogen Dioxide

100%
Tyszkiewicz C., Karasiński P., Rogoziński R.
Acta Physica Polonica A
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2012
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vol. 122
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issue 5
915-920
EN
The sol-gel technology allows preparation of the thin silica films ranging in porosity from dense to highly porous. These films can function as matrix binding molecules of pH-sensitive indicators and can be utilized as sensitive coatings for intensity based planar evanescent wave chemical sensors. This paper is devoted to manufacturing technology and characterization of highly porous silica films deposited on soda-lime glass substrates, impregnated with bromocresole purple and cresole red. Two different methods of impregnation were used: dip coating, which entails sensitization of both silica films deposited on each side of a substrate and selective deposition of a dye solution on single side of the substrate. Manufactured sensitive films were tested toward influence of gaseous ammonia and nitrogen dioxide on their spectral characteristics of the absorption coefficient and the imaginary part of the refractive index. It was shown that bromocresole purple allows detection of both gases: NH_3 and NO_2.
11
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Physical Characterization of Sb_2O_3-M_2O-MoO_3 (M~= Li,~K) New Glasses

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Soltani M., Hamzaoui M., Houhou S., Touiri H., Bediar L., Ghemri A., Petkova P.
Acta Physica Polonica A
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2013
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vol. 123
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issue 2
227-229
EN
New heavy metal oxide glasses involving Sb_2O_3 have been investigated. By using classical routes (melting-casting), glasses synthesized in silica crucibles were obtained in the combination of ternary systems Sb_2O_3-M_2CO_3-MoO_3 (M = Li and K). Characteristic temperatures such as glass transition T_{g}, and onset of the crystallization T_{x}, have been measured using differential scanning calorimeter. Ultrasonic velocities were measured by using pulse echo method to determine the elastics parameters, such as elastic modules (E, G, K, L). Other physical properties were measured, such as density and optical transmission window in far infrared spectra using KBr pellets. Influence of composition on these physico-chemical properties is discussed and correlated to the glass structure.
12
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Effect of Wet Etching of Arc-Induced Long-Period Gratings on Their Refractive Index Sensitivity

100%
Myśliwiec M., Grochowski J., Krogulski K., Mikulic P., Bock W., Śmietana M.
Acta Physica Polonica A
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2013
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vol. 124
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issue 3
521-524
EN
The paper presents highly refractive index sensitive operation of long-period gratings enhanced by wet etching of the fiber cladding. Long-period gratings with period of 283 μm were induced in Corning SMF28 optical fibre using electric arc technique. Then etching in hydrofluoric (HF) acid solution has been applied to improve operation of the sensor. Sensitivity improvement effect induced by fiber cladding reduction has been numerically simulated. The developed numerical model enables quick estimation of cladding thickness reduction essential to achieve dispersion turning point. At this point long-period gratings reaches maximum sensitivity to external medium refractive index. Simulation showed that dispersion turning point for this long-period grating is achieved by cladding thickness reduction of 1.7 μm. We obtained good simulation match with experimental results, where approximately the same thickness was etched. The refractive index sensitivity of the long-period grating-based sensor has been improved by factor of 5. Since long-period grating period is limited when using electric arc fabrication method, this physical limitation makes difficult achievement of dispersion turning point and reaching maximum sensitivity of the long-period grating. We show that sensitivity of electric arc induced long-period grating can be significantly improved by post processing techniques such as wet etching.
13
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Analysis of Long Period Gratings in the Gradient Structures of Planar Waveguides

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Kotyczka T., Rogoziński R.
Acta Physica Polonica A
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2013
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vol. 124
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issue 3
486-489
EN
This paper introduces the application possibilities of long-period waveguide gratings produced in gradient structures of planar waveguides and their possible usage as the detectors of changes in the refractive index. The influence of technological processes and corrugation's parameters on the resonant characteristics and transmission spectrum (obtained by the numerical simulations) of such structures was presented. The influence of changes in the refractive index of the environment on the transmission spectral characteristics was shown. The possibilities of sensor applications of such structures was presented as well. The calculations were performed for two types of gradient waveguides' structures: produced in BK7 glass with the use of K^+ ↔ Na^+ ion exchange and produced in soda-lime glass with the use of Ag^+ ↔ Na^+ ion exchange.
14
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Urbach's Rule in Undoped and Co Doped (80-x)Sb_2O_3-20Na_2O-xWO_3 Glasses

100%
Petkova P., Soltani M., Petkov S., Nedkov V.
Acta Physica Polonica A
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2012
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vol. 121
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issue 1
152-154
EN
We have analyzed the Co influence on the absorption spectra of (80-x)Sb_2O_3-20Na_2O-xWO_3 glasses in the Urbach rule region at room temperature. We present the comparison between Co and WO_3 manifestation in the spectral region 2.64-3.14 eV. The spectral characteristics of "crystalline" and "glassy" Urbach's rule are also calculated.
15
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Temperature Cross-Sensitivity for Highly Refractive Index Sensitive Nanocoated Long-Period Gratings

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Grochowski J., Myśliwiec M., Mikulic P., Bock W., Śmietana M.
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EN
There is a demand for highly refractive index sensitive devices simultaneously insensitive to temperature (T) changes. We investigate both T and refractive index sensitivity of long-period gratings coated with 100 nm thin high refractive index (n ≈ 1.9 at λ = 1550 nm) silicon nitride (SiN_{x}) film. The long-period gratings with period of 500 μm were induced in standard Corning SMF28 fibre using electric arc and nanocoated with SiN_{x} by radio frequency plasma enhanced chemical vapour deposition method. As a sensorial effect we investigated resonance shift with temperature variations (from 30 to 70°C) for measurement in deionized water (n_{D} = 1.33) and glycerine (n_{D} = 1.46). In case of measurements in water for resonance observed at λ = 1510 nm, refractive index sensitivity of - 85 nm/RIU and temperature sensitivity of 0.09 nm/C (H_2O) were obtained which gives refractive index-T sensitivity ratio (RI/T) of - 944°C/RIU. Refractive index and T sensitivity of sensor covered with SiN_{x} film increased to - 618 nm/RIU and 0.22 nm/°C, respectively. Thanks to nanocoating deposition, refractive index-T sensitivity ratio was improved by factor of 3. In case of measurements in glycerine significant influence of glycerine's thermo-optic coefficient on obtained results was observed. It is worth noticing that SiN_{x} coating stabilizes sensing behaviour of the sensor.
16
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Planar Evanescent Wave Ammonia Sensor - Influence of Refractive Index Profile on Sensor Properties

100%
Karasiński P., Tyszkiewicz C., Rogoziński R.
Acta Physica Polonica A
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2011
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vol. 120
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issue 4
651-656
EN
The paper presents the results of the investigations involving the influence of the change of launching conditions on the characteristics of the planar amplitude evanescent wave ammonia sensors. Investigated sensors are based on the channel gradient waveguides, which are produced with the application of the ion exchange in glasses. In our investigations we have tested two sensor structures of different refractive index profiles. The absorption sensitive films were produced using sol-gel technology.
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