Heidenhofstraße 8
D - 79110 Freiburg
Tel.: +49 (0)761 8857-0
Fax +49 (0)761 8857-224
Max-Planck-Institut für Mikrostrukturierung (MPI)
Weinberg 2
06120 Halle
Germany
Tel: 0345-5582-654 (A. Ebensing)
Fax: 0345-5582-557
B. Hundrieser
birgit.hundrieser@ipm.fraunhofer.de
Dr. P. Hahn
peter.hahn@ipm.fraunhofer.de
Many gases (and liquids) exhibit characteristic absorption lines in the mid infrared wavelength region (3-20 µm). So spectroscopic-based sensor techniques play a major role in processing and production measurement (e.g. CO and CO2 measurement in the automotive market) but with the major drawback of high costs for such systems.
The aim of this project is to evaluate and develop sensors on the basis of photonic crystals for spectroscopic detection of gases. The advantage of such systems over conventional ones could be the possibility of miniaturization, integration, batch processing and thus low-cost versions of such sensor systems.
Macroporous silicon is intended to be used as photonic crystal material, from which structures for wavelength in the mid infrared region can be fabricated with great reproducibility. Besides the lateral lithographic structuring also a structuring along the pore axis is possible: The diameter of the pores depends on the etching current which is controlled by the rate of hole generation. A periodic variation of the backside illumination results therefore in a periodic variation of the pore diameter with the pore depth (see figure). Together with the 2D lateral periodicity of the pore array these modulated pores form a 3D photonic crystal. Although it does not exhibit a complete 3D bandgap the structure has the advantage that the modulation period along the pore axis (z-axis) can be independently controlled from the periodicity in the x-y-plane. Consequently, the dispersion relation along the pores can be adjusted nearly independently from the dispersion relation perpendicular to them. By this, it is possible to vary the energetic position of the bandgap without designing an appropriate lithographic prepattern.
Theoretical calculations are necessary regarding the structure layout (tailoring of the sensor geometry for the desired wavelength, layout of the coupling regions). Beside the experimental verification of the effects predicted from theory it is the main goal of this project to work out practical solutions for sensors.
Projectleader: R.B. Wehrspohn (MPI Halle) und A. Lambrecht (FhG IPM Freiburg)
Team: J. Schilling, S. Schweizer, S. Matthias (MPI Halle); A. Lambrecht, P. Feisst, and P. Hahn (FhG IPM, Freiburg)
Cooperation: V. Sandoghdar (ETH Zürich), Dräger AG (Lübeck)
Funding: DFG in the framework of the Schwerpunktprogramm "Photonische Kristalle" under WE 2637/2-1; LA 1342/1-1
Patent: 10063151.7 (Aktenzeichen Dt. Patentamt) bzw. PCT/EP01/14802 (PCT-Nummer)
SPP meeting, March 2002, Bad Honnef
Zurück/Back