Investigation on the generation of photonic crystals using two-photon polymerization (2PP) of inorganic-organic hybrid polymers with ultra-short laser pulses

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In the framework of the proposed project, a novel and flexible technique for the generation of photonic structures or demonstrators, respectively, will be realized by means of two-photon polymerization (2PP) of inorganic-organic hybrid polymer (ORMOCER) resins by irradiation with femtosecond laser pulses. This technique enables one to generate any 2D or 3D photonic crystals with structural dimensions of approximately 100 nm as well as to generate integrated systems of 2D or 3D photonic crystals including waveguides to connect the crystals to any standard characterization equipment. Inorganic-organic hybrid polymers are transparent for visible or near-IR laser light. If the laser light reaches a particular threshold intensity, the organic cross-linking of the resins monomers can be initiated due to two-photon absorption. This threshold intensity is achieved for strongly focussed, ultrashort (~10-13 sec) laser pulses at a moderate average power (less than 100 mW). If the focus is moved three-dimensionally within the resin, polymerization along the path of the focus occurs. Since 2PP has a well-defined threshold fluence, lateral and vertical structures can be generated with a suitable set of parameters such as, e.g., pulse energy and pulse number, which are below the diffraction limit of the focus volume of the laser radiation.