Multimode Interference Structures of Variable Geometry for Optical Sensor Application

Abstract

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.

Improvement of sensitivity for hybrid fiber optic sensor for application in perimeter protection

“…This system combines the features of a classical interferometer and modalmetric sensor offering in results new properties. Such systems are tested by many groups of scientists and literature publications can be found on the research [1][2] and the application of such systems [3][4]. In the authors field of interest is using this type of sensor to protection systems, where the most important task is to detect as early as possible an intruder.…”

Differential interference in a polymer waveguide

“…ion exchange, plasma-enhanced chemical vapour deposition (PECVD) and spin coating in the case of SU8-polymer waveguides [1][2][3][4][5][6][7][8][9][10][11].…”

The Waveguide Structure Based on the Polymer SU8 on a SiO2/Si Substrate

“…Planar waveguide structures may be obtained by means of many techniques, among others by ion exchange in glass, chemical deposition of the layer from the gaseous phase applying plasma (plasma enhanced chemical vapour deposition, PECVD), magnetron sputtering or the formation of thin polymer layers by spin coating [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. In the investigations dealt with in this paper the waveguide structures were obtained by spin coating.…”