Optical waveguides are normally sensitive to the various inhomogeneities inside the waveguide and also to the surrounding media and surface contaminations. Various sensor systems were developed on this principle. One of the most sensitive and effective systems is the optical waveguide lightmode spectroscopy (OWLS). The necessary OWLS sensor chips were developed on the basis of Silicon-Titanium-Oxide (Si_1-xTi_xO₂), containing a grating for incoupling of laser light into the waveguide layer. The incoupling angle dependence of the photocurrent is measured. This basic waveguide layer can be covered with further solid layer in order to sensitise for selected specific applications. The sensor chips can be sensitised also for label free microbiological investigations. OWLS method allows not only qualitative, but also quantitative detection of biological species.

The electrochemical methods, on the other hand, are widely used both in inorganic and organic chemistry, and also advantages in microbiology were demonstrated.

In this work first results are presented in combination of these two methods for simultaneous measurement of refractive index changes of the waveguiding system and electrical current changes due to the presence of the cells/molecules/ions to be investigated. An Indium-Tin-Oxide (ITO) nanolayer is deposited and activated on the top of the sensor chip. ITO is known as n-type conductor. This electrically conductive oxide layer serves as working electrode in the specially developed electrochemical cuvette.

The basic results are demonstrated using H₂O₂ and toluidine blue solutions, using KCl and TRIS solutions as buffer and transport media. Measurements show the changes of the incoupling angles and that of the effective refractive indices (both electrical and magnetic modes) with the changes in buffer solutions and with the injection of other solutions and species to be studied and also on the applied potential in cyclic and chrono voltammetric measurements.