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

在该项目框架内，将利用飞秒激光脉冲辐照无机-有机杂化聚合物（ORMOCER）树脂的双光子聚合（2PP），实现一种新颖而灵活的光子结构或演示体生成技术。该技术可以生成结构尺寸约为100纳米的二维或三维光子晶体，也可以生成二维或三维光子晶体的集成系统，包括将晶体连接到任何标准表征设备的波导。无机-有机杂化聚合物对可见光或近红外激光是透明的。如果激光达到一个特定的阈值强度，树脂单体的有机交联可以启动由于双光子吸收。该阈值强度是实现强聚焦，超短（~10-13秒）激光脉冲在中等平均功率（小于100兆瓦）。如果焦点在树脂内三维移动，聚合沿着焦点的路径发生。由于2PP具有明确的阈值通量，因此可以使用一组合适的参数，例如脉冲能量和脉冲数，生成横向和纵向结构，这些参数低于激光辐射聚焦体积的衍射极限。

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.