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1
Content available remote

MMI Structures Covered by Bromocresol Purple for Ammonia Detection

100%
Szewczuk A., Błahut M.
Acta Physica Polonica A
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2013
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vol. 124
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issue 3
570-573
EN
In the paper examinations of a lightguide sensor on the base of gradient index multimode interference structures are presented. Investigated structures were fabricated in potassium-sodium ion exchange process. Multimode interference sensor was designed for ammonia detection. Bromocresol purple covering the multimode section was used as a sensing layer. Numerical calculations were performed with the use of modal analysis and beam propagation method to optimise sensor geometry and sensing layer thickness. Experimental results show the possibility of ammonia detection from the concentration of tens ppm.
2
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Sensing Properties of Four-Layered Planar Waveguides - Theoretical Analysis

100%
Tyszkiewicz C.
Acta Physica Polonica A
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2012
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vol. 122
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issue 5
908-914
EN
Optical waveguides are the fundamental components of chemical and biochemical evanescent wave sensors. Presented work focuses on the theoretical investigations of homogeneous sensitivity of four-layered composite planar waveguide composed of a silica-titania film and a titania film deposited on a glassy substrate in order of citing. Characteristics of a homogeneous sensitivity and a fundamental modes homogeneous sensitivity difference of such a structure are compared with the ones for a three-layered waveguide composed of silica-titania waveguiding film. Therefore the influence of a high refractive index titania film on homogeneous sensitivity characteristics of three-layered structure is given. It was shown that homogeneous sensitivity difference of fundamental modes of four-layered waveguide can be optimized with respect to thicknesses of each layer. For each value of a cover refractive index there exists the minimal thickness of the titania layer which maximizes the homogeneous sensitivity difference of fundamental modes.
3
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Inverted Rib Waveguides - Theoretical Analysis of Sensing Properties

100%
Tyszkiewicz C.
Acta Physica Polonica A
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2013
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vol. 124
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issue 3
582-585
EN
Optical waveguides are fundamental components of chemical and biochemical evanescent wave sensors. Presented work is devoted to theoretical investigations of homogeneous and surface sensitivity characteristics of the inverted rib waveguide structure. The inverted rib waveguide discussed in this paper is composed of an ion-exchange based channel waveguide formed in a glassy substrate and a uniform, high refractive index, sol-gel derived SiO_2-TiO_2 film. Characteristics of a homogeneous sensitivity, a surface sensitivity and fundamental modes sensitivity differences in function of a uniform film thickness and a maximal refractive index contrast of the gradient index channel waveguide are given. The influence of the SiO_2-TiO_2 film thickness on sensitivity characteristics is discussed. The analysis is carried out on a bases off the effective index method used with the transfer matrix method.
4
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Application of Multilayer Planar Waveguide Structures to Sensing

100%
Auguściuk E., Dziąg D.
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issue 6
1081-1086
EN
The multilayer planar step index waveguides have been studied in detail for many years now. We examined gradient index waveguide, which was not thoroughly studied. In this article we have studied structures made from three, four, and five layers. We also used different substrates for this experiment. Gradient index waveguides were made in Bk7 and Gevert's glass by the ion-exchange method. Then we put on it a thin layer of polymer and examined it again. Afterwards we applied a second layer of polymer achieving five-layer planar waveguide. Layers deposited on gradient index waveguide change the propagating conditions of light beam in waveguide structures. Using a generalized m-line spectroscopy method we determine thickness and refractive index of each layer of waveguide structure. In the next step, a simulation for step index planar waveguides was run. The values for each layer were taken from previously calculated thickness and refractive index for multilayer gradient index waveguides. Beam propagation method was used to obtain N_{eff} only for step index waveguide structures to compare with N_{eff} of gradient index waveguide structure. The changes in propagation of a light beam not only in waveguide (several modes) layer may be applied to sensing and controlling the direction of light in the waveguide structure (by depositing on it a polymer layer with the appropriate refractive index).
5
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Long Period Waveguide Gratings in Planar Gradient Waveguides

80%
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.
6
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Silicon Nitride Overlays Deposited on Optical Fibers with RF PECVD Method for Sensing Applications: Overlay Uniformity Aspects

80%
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.
7
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Model of Optical Sensor on the Base of MMI Structures

80%
Szewczuk A., Błahut M., Pyka W.
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issue 6
1250-1253
EN
The paper presents the research on waveguide sensors based on multimode interference structures. In the modeled systems, the applied sensor layer was used as the cover of the multimode section. The cover of the multimode section can be made of material sensitive to the changes of definite external conditions, and through a proper selection of this material the sensor can be adapted to the detection of various physicochemical quantities. In effect of the changes of optical parameters of the sensor layer, the propagation conditions change, which can be easily observed in the location changes of N-fold images of the input field. In the paper we have investigated and compared the systems based on waveguides having step index profile and gradient distribution of refractive index. We have demonstrated that the sensitivity of such systems can be adjusted through a proper selection of the dimensions of the multimode section.
8
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Multimode Interference Structures of Variable Geometry for Optical Sensor Application

80%
Szewczuk A., Błahut M.
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issue 6
1254-1258
EN
The paper presents the analysis results of a waveguide sensor based on multimode interference structures. The multimode section was covered with sensor material. The change of optical parameters of the cover entails the change of propagation conditions of light in the structure. By measuring the light intensity at the output of the structure, we can define external physicochemical parameters to which the sensor layer is sensitive. The paper presents the method to adjust the sensitivity of the device through a proper selection of the thickness of the particular layers of multimode waveguides. We present, among others, the analysis results of optical systems whose parameters of the sensor layer corresponded with the parameters of wolfram oxide (WO_3), being the material frequently applied as a gas-sensitive layer in gas sensors. We have proposed a configuration of a sensor based on the Mach-Zehnder interferometer whereof one arm is a multimode section and the other one a single mode waveguide. The detection method was narrowed down here to the measurement of phase difference between the waves propagating in the respective arms.
9
Content available remote

Applications of Gradient Index Multimode Interference Structures in the Technology of Optical Sensor

80%
Szewczuk A., Błahut M.
Acta Physica Polonica A
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2011
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vol. 120
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issue 4
740-743
EN
The aim of the work is the presentation of operating principle and properties of multimode interference structure devices made in gradient index technology by K^{+} and Na^{+} ion exchange method from the point of view of optical sensor design. Numerical analysis was performed using beam propagation method. Analyzed sensor structures are covered by nanolayers whose refractive index higher than the multimode interference section index is the reason for the concentration of wave propagation energy in the sensor layer area and its vicinity. Modifications of external propagation conditions change the refractive index and extinction coefficient of a sensor layer. The variation of optical properties leads to the modification of waveguiding conditions in the multimode interference coupler.
10
Content available remote

Gradient Index Multimode Interference Structures - Technology and Applications

80%
Błahut M., Kasprzak D.
Acta Physica Polonica A
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2009
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vol. 116
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issue 3
257-260
EN
The aim of this paper is to present the operating principles and properties of gradient index multimode interference structures made by K^{+}-Na^{+} ion exchange in glass and their basic applications in optoelectronic circuits. The investigations of multimode interference structures were performed applying a method based on the visualization of light distribution in gradient structures, using fluorescence of the substance covering the multimode interference structures section. Basing on the above we present gradient index multimode interference structures applications in splitters and couplers 1× N technology of different configurations.
11
Content available remote

Effect of Wet Etching of Arc-Induced Long-Period Gratings on Their Refractive Index Sensitivity

80%
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.
12
Content available remote

Analysis of Long Period Gratings in the Gradient Structures of Planar Waveguides

80%
Kotyczka T., Rogoziński R.
Acta Physica Polonica A
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2013
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vol. 124
|
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.
13
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Temperature Cross-Sensitivity for Highly Refractive Index Sensitive Nanocoated Long-Period Gratings

80%
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.
14
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Silica-Titania Films Fabricated by Sol-Gel Method for Applications in Planar Photonics

70%
Karasiński P.
Acta Physica Polonica A
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2009
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vol. 116
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issue S
S-114-S-116
EN
The work presents silica films produced with sol-gel method of extremely different refractive indices as well as two-component waveguide films SiO_{2}:TiO_{2} of very low attenuation.
15
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Content available

Optoelectronic Device Based on Gunn Effect Extended Diode Structure

70%
Tralle I.
Acta Physica Polonica A
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2007
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vol. 111
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issue 6
835-846
EN
We discuss the possibility of light control by means of light diffraction by space charge waves which are the periodic domain trains induced at some circumstances in GaAs Gunn effect diode. The two possible regimes of the proposed device are considered: the first one which is analogous to the Bragg diffraction in case of light-acoustic diffraction and the other one, which we call "intermediate", since the parameter Q which distinguishes the Raman-Nath (Q<1) and the Bragg diffraction (Q>10), in this case is≈1 (actually, only bit smaller than 1). Among the advantages of this hypothetical device are the simpler control of operation and perhaps, possibility to couple it with the waveguides and switchers for surface electromagnetic waves and other miniaturized photonic circuits.
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