Femtosecond laser processing, microstructuring of transparent polymers for Lab-on-Chip applications

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In recent years, the IQ group has succeeded in using intensive localized femtosecond laser irradiation to demonstrate material modifications and thereby local refractive index increases in the interior of polymer substrates and films and to establish this technique as a reproducible and reliable method. Waveguides of different types with single mode attenuation values below 0.5 dB/cm could be demonstrated. Thus, all previous literature values have been undercut by almost one order of magnitude. The new project focuses on the practical use of femtosecond waveguides and the realization of novel complex waveguide structures under consideration of the full 3D capability of the process. The propagation scattering losses are to be further reduced by beam position stabilization during writing, and software-controlled focus shaping is to be realized by using a transverse phase modulator (SLM) in the writing beam. This enables simultaneous femtosecond laser writing with several adjacent and interrelated foci. By changing the phase mask at the SLM during the writing process, complex 2D and 3D coupler structures can be realized in one go. The first steps towards a 'mobile lab' based on a processed polymer film, which is transparently placed over the display of a smartphone/tablet, are the result. A network of waveguides running in the film is fed individually in multiple colors from the display and transports the light to the front camera, where it is detected sensitively and color resolved. In this way, sensors distributed over the film can be read flexibly. Finally, hollow capillaries can be written in polymer substrates as microfluidic channels with the same femtosecond laser writing setup. Combined with the optical waveguides, an individual integrated lab-on-a-chip is created in a single production step.