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).
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.
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.
The paper presents the technology and testing measurements of Mach-Zehnder interferometer made by K^{+}-Na^{+} ion exchange in glass. As a splitter and coupler of measuring and reference arms we used gradient index multimode interference structures in symmetrical configuration. The investigated interferometer, working in asymmetrical configurations, registers the phase shifts resulting from the changes of refractive index of the cover of both interferometer arms.
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.
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.
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