A fully automated system has been developed for microscope-based single particle analysis by extracting optical finger-prints from individual particles in ambient air samples. For this purpose, light microscopy was developed towards an objective measuring technique by employing a novel pattern recognition technique. Automated particle classification is based on so-called grey scale invariants, extracted from microscopic images of translucent, fluorescent and dark field microscopy. This information was bundled to a feature vector providing a kind of finger print for every particle. In a first step this approach was used for an automated recognition of allergen carriers such as pollen and fungal spores. A leave-one-out test gave a recognition rate of about 95% for 26 for the most frequent pollen species in central Europe. Because no pollen-specific code was used, the recognition software was also employed for an automated recognition of fungal spores without any change. Six of the most frequent airborne fungal spore genera in Central Europe were classified with a mean recognition rate of 93%. These results gave reason to a research project aiming at the development of a fully automated system. The instrument should combine (1) high-volume sampling of coarse particles >2.5 μm, (2) electrostatic precipitation of this fraction onto a surface suitable for optical analysis, (3) automatic preparation for microscopic single particle analysis, (4) imaging by various microscopic techniques, e.g. transmitted, fluorescence and dark field microscopy, (5) feature extraction by grey scale invariants, (6) classification by self-learning Support Vector Machines and (7) hourly output of number concentration of airborne pollen, fungal spores and other particles of interest. A first demonstrator is presented in early 2005. First field tests are planned for the first half of 2005. A commercialised device should be available as from 2007. The project is funded by the German Ministry of Education and Research.

The detection of hybridization events on oligonucleotide microarrays in real time can be performed, using the optical principle of total internal reflection fluorescence (TIRF). We have investigated and compared three TIRF-sensing configurations using two bulk and one integrated optical planar waveguide as transducer platforms for oligonucleotide microarrays, which have been brought in contact with flow cells. Based on the ray optics model, expressions were derived for the calculation of the intensity of the CCD-camera signal generated by solved fluorophores in the flow cell volume. A noise analysis was performed and expressions for the calculation of the detection limit of the surface fluorophore density were derived. With a bulk optical single total internal reflection configuration a detection limit of 3.74molecules/μm2, with a bulk optical multiple total internal reflection configuration a detection limit of 1.83molecules/μm2 and with the integrated optical waveguide (IOW) configuration a detection limit of 0.013molecules/μm2 was numerically estimated based on background data of the bulk volume signal. The derived analytical expressions address the full system, including light source, optical waveguide and the detection unit and can serve as a tool for TIRF-system design.

This paper describes the development of an optical readout system for the real-time analysis of fluorescent-labeled DNA microarrays is described. The system is targeted toward research applications in genomics, agriculture, and life sciences, where the end-point detection of state-of-the-art readout systems does not provide sufficient information on the hybridization process. The hybridization progress of molecules from the liquid phase in a flow cell to immobilized oligonucleotides on a transducer surface can be observed. The excitation of fluorochromes is realized by a semiconductor laser, and the fluorescence emission is collected by a cooled CCD camera. Quantitative data can be extracted from the images for analysis of the microarray. For the signal transduction, the principle of total internal reflection is used. With a multiple internal reflection arrangement, the sensor chip was adapted to the standard microscope slide format and a homogeneous evanescent illumination of the active area of the sensor surface was achieved. An application measurement was carried out with this readout system. The hybridization of Cy5-labeled 30-mer single-stranded oligonucleotides to fully complementary immobilized strands was observed in real time. A kinetic analysis was demonstrated with the recorded data. Melting curves of a 140-mer PCR product from a hemochromatosis patient sample hybridized to immobilized wildtype mutant 15- and 17-mer oligonucleotides were recorded and single-point mutations could be detected.

An integrated-optic Bragg-cell based on diffraction of light by a surface acoustic wave (SAW) was fabricated on glass with a piezoelectric ZnO-layer. The ZnO-film was deposited by RF-magnetron sputtering. To generate a SAW an interdigital electrode array is needed, which is positioned between the glass and the ZnO-film. Such a ZnO-transducer has been tested by the standard RF-measurment techniques for+ SAW filters. The optical waveguides were produced by thermal K -ion exchange in BK7-glass. A special waveguide structure with two intersecting waveguides was used. For increasing the interaction length in the crossing area the monomode waveguides were tapered adiabatically up to a width of 50μm. The diffraction efficiency of such a Bragg-cell in glass was measured to be about 4%-5% at an RF input power of 1W.

Computer aided measurement systems for the determination of nearfield intensity profiles, insertion loss, waveguide attenuation by Fabry-Perot resonance and refractive index profiles by effective indices have been developed. The repeatability and accuracy of the measurements have been analyzed.

Integrated optical directional couplers with parallel waveguides1 have large device lengths due to the guide separation regions. Curved/straight waveguide transitions cause excess loss. In this paper we present passive couplers with circular waveguides. We investigate the following structures shown in Fig. 1: an asymmetric coupler consisting of a curved and a straight guide (a); a symmetric coupler with two oppositely curved guides (b) with the coupling distance d0 (center to center) at z = 0. In contrast to parallel guides the phase fronts of both guides are tilted with respect to each other. Thus mode coupling occurs along curved phase planes with the effective distance d(z).2

The losses of curved waveguide structures have been analyzed with respect to optimal S-bend design. Directional couplers consisting of curved waveguides fabricated by ion-exchange in glass have been investigated. A theoretical model for the coupling ratio with good agreement to the experimental results has been derived.

An optical measurement system will be presented which allows the continuous recording of radiation induced optical loss and thermoluminescence signals during and after irradiation. The complete optical system can operate in the spectral range from 0.6 to 1.7 μm. This allows the detection of the following absorption and scattering processes: elec-tronic transitions, Rayleigh-scattering and vibrational modes. Measurements on typical fibers will be shown. The measurements are performed in order to examine the influence of lowest exposure levels and to evaluate the application in dosimetry systems.