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Integrated optics concerns mainly the generation, guiding, and detection of light. Especially bio sensing needs systems that incorporate electronic and photonic devices for the detection of harmful substances, like synthetic estrogens or plasticizers. We present recent developments in the integration of Si-based light emitters into a photonic circuit for a planar optical waveguide-based bio detection system. The growing demand for sensitive biochemical sensors in the environmental control, medicine or process technology results in the development of integrated sensors, which should show a high resolution over a wide concentration regime. In our first approach we deal with the integration of a Si-based light emitting device (LED) into a photonic circuit for the detection of harmful biological substances. Light injection into a waveguide is commonly obtained by using an external source coupled to the waveguide, e.g. an optical fiber via total internal reflection. For simplifying this injection process, we built Si-based LEDs consisting of a metal-oxide-semiconductor (MOS) structure, in which the oxide film contains group-IV and/or rare earth elements, incorporated by ion-beam synthesis [1, 2]. The Si-based LED exhibits strong electroluminescence, tunable from the visible up to the UV region depending on the rare-earth element (e.g. Gd, Tb, Eu, Nd, Er). Currently, the Si-based LEDs are already available and best efficiencies were achieved by Tb or Er implantation with an external quantum and power efficiency of 16% and 0.3%. LOCOS (local oxidation of silicon) processing and an additional layer of SiON were applied to the device to improve the electrical stability and operation time. Our concept bases upon a Si-based photonic circuit which consists of the integrated LED, working as the light source, a newly fabricated dielectric strip-waveguide below a bioactive layer and a receiver. The dielectric strip-waveguide has a Si3N4 or SiON core, in which the light should be guided, and a cladding of SiO2. The receiver should be a photodiode (e.g. Ge, Si). In this work, we focus on the development and characterization of the dielectric waveguides. For theoretical pre-analysis we are using the finite element method by the FlexPDE software for calculating the mode profiles and resonance frequencies according to the cross sections of the structures. The fabrication of the waveguides was done by plasma enhanced chemical vapor deposition (PECVD), photolithography and electron beam lithography. Obtained SEM results enabled an improvement of the fabrication recipe of the waveguides by using an additional Al-masking during the reactive ion etching (RIE). Furthermore, a new measurement setup is built up, which enables transmission measurements and the inspection of the beam profiles as well as the damping factors of the structures in dependence on their cross sections. In future, the theoretical calculations are going to be compared with the experimental results of transmission and beam profiling measurements. Moreover, the Si-based LED should be coupled with the waveguide e.g. by Bragg grating. Finally, this lab-on-a-chip system is showing a high potential to become an all-round applicable integrated sensor system, without using any external light sources or relay lenses, which is why it should be easily portable and customizale.

Integrated optics concerns mainly the generation, guiding, and detection of light. Especially biosensing needs systems that incorporate electrical, electronic, and photonic devices for the detection of harmful substances, like synthetic oestrogens or plasticizers. We present here recent developments in the integration of our Si-based light emitter into a photonic circuit for a planar optical waveguide-based biodetection system.

In this report we present our recent developments for utilizing the Si-based light emitter consisting of a MOS structure for the detection of organic pollutants. In the latest approach the light emitters are intended to serve as light sources in smart biosensors [1, 2]. In fluid media the device is placed beneath the dye-labeled sample exciting the dye. This light emission can be recorded by an external detector. It was shown that the silanization of the device surface was successfully based on the covalent binding of the organosilane [3]. The harmlessness of the silanization method to the integrated light emitters was proved by comparing the electroluminescence spectra of Tb-based MOSLEDs before and after silanization. We further showed that the transparency is maintained. Similarly, the human estrogen receptor hERα could be immobilized effectively on the coated surface [3]. We also discuss our concept of an integrated light emitter and a receiver in a dielectric waveguide structure below the bioactive layer for the detection of harmful substances, like synthetic estrogens or plasticizer in drinking water. Optical properties of waveguides, e.g. the transmission, are very sensitive to changes of the effective refraction index, which might be induced by the immobilization of biomolecules on the waveguide surface or in cavity structures, e.g. photonic crystals. This lab-on-a-chip system provides fast light transmission without using of any additional lenses and achieves further portability and miniaturization. [1] L. Rebohle, C. Cherkouk, S. Prucnal, M. Helm, W. Skorupa, Vacuum 83, 24 (2009) [2] L. Rebohle, T. Gebel, R.A. Yankov, T. Trautmann, W. Skorupa, J. Sun, G. Gauglitz, R. Frank, Optical Materials 27, 1055 (2005) [3] C. Cherkouk, L. Rebohle, W. Skorupa, T. Strache, H. Reuther and M. Helm, Journal of Colloid and Interface Science 337, 375 (2009)

A different silanization method for SiO2 surfaces has been raised for Si-based light emitter which are considered as light sources in sensors for the detection of harmful biomolecules. This approach uses a special experimental setup for gas phase silanization (GPS) and is based on the evaporation and deposition in nitrogen atmosphere at normal pressure for 15 minutes with different silane volumes. The light emitter has a SiO2 passivation layer on the top which was hydrolyzed in an in situ hybridization chamber and catalyzed with MES (2-(N-morpholino)ethanaesulfone acid hydrate) buffer solution. Afterward, the substrates were silanized with the GPS method using the organosilane (3-Aminopropyl)trimethoxysilane (APTMS). Infrared spectroscopy, X-ray spectroscopy and Atomic force microscopy were used to control and characterize the structure of the SiO2 surface and the APTMS layer. The results demonstrate a successful covalent binding of the coupling agent and the interaction of the deposited molecules with each other. The roughness of the modified surface was investigated by the Atomic force microscopy. The silanized samples show rough and textured surfaces. At last, the suitability of the developed GPS method was verified on light emitters.