Forschungs- & Entwicklungsinformationsdienst der Gemeinschaft - CORDIS

Technology for mach-zehnder interferometric sensor chips

The contribution of the ORC to the project was the development of integrated optical sensor devices that showed sensitivity to target agents such as humidity, alcohols and butane. They were based on waveguiding Mach-Zehnder interferometers fabricated via ion-exchange in soda lime glass chips as well as via laser writing in hybrid organic/inorganic chips produced by sol-gel.

They were operating on the principle of Mach-Zehnder interferometers and had one reference and one sensor output. After fabrication the chips were coated by an isolation layer of sputtered silica apart from a window on the sensing arm of the interferometers, which limits the spatial extent of the interaction of the guided light with the sample. In other words the interaction of the guided light with the sample was restricted to the region in the window.

The whole chips were then coated with thin films materials sensitive to the target agent in order to increase the sensitivity of both the MZIs and the exposed reference waveguide. The thin films were single-mode planar waveguides with a thickness just below the cut-off condition for the TE00 mode.

This led to an enhancement of the evanescent field and subsequently to an improvement of the sensitivity so that the high index film practically served as the sensing regions of the chip. The chip design for a 10-mm-long window allowed precise measurement of very small refractive index changes (down to n~10-7) by observing changes at the outputs of the inteferometric pattern.

The materials were deposited on the window areas using various techniques such as pulsed laser deposition, reactive sputtering, spin coating, casting and spray coating techniques by the consortium partners. Layers of the following materials were then deposited on the widows:

"Active layers of indoleacetic acid (IAA) doped with gold (Au) with thicknesses varying from 400 nm to 3 microns for alcohol detection
"SnO2 and ZnO layers layers with a thickness between 25 and 30 nm
"Polyethylene oxide for alcohol detection.
"Polymethyl [4-hydroxy-4,4bis(trifluoromethyl)butyl] siloxane (PLG) with a thicknens in the range of 5 to 10 nm.

In all our achievement was the development of innovative approaches an to produce miniaturized integrated optical devices for sensing of various chemical agents with advanced sensitivity and stability with potential for implementation in various application areas and particularly in industrial environments and security.

Reported by

University of Southampton
SO9 5NH Southampton
United Kingdom
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