Abstract
A method is reported for improving the spatial resolution and engineering the stop gaps of the inorganic-organic 3D woodpile photonic crystals (PhCs). The approach is based on the two-photon polymerization (2PP) of an inorganic-organic hybrid material and a post-thermal treatment (PTT) process. The effects of PTT on polymerized 1D, 2D and 3D structures have been characterized. Ultimately, the feature size of the suspended rods has been reduced to approximately 33 nm and the spatial resolution of inorganic-organic 3D woodpile PhCs has been improved from approximately 150 nm to approximately 86 nm. The approach is also demonstrated as a powerful tool to engineer the stop gaps of 3D PhCs. In particular, a combination of PTT and the threshold fabrication technique leads to the stop gap of a 3D woodpile PhC that can be tuned over a large wavelength range of approximately 318 nm from the near-infrared to visible region.
Highlights
Direct laser writing (DLW) is an effective and flexible approach to inducing two-photon polymerization (2PP) in various photoresists and has been intensively studied for the fabrication of three-dimensional (3D) arbitrary micro-structures including 3D photonic crystals (PhCs) [1,2,3,4,5,6,7,8,9,10]
A combination of post-thermal treatment (PTT) and the threshold fabrication technique leads to the stop gap of a 3D woodpile PhC that can be tuned over a large wavelength range of 318 nm from the NIR to visible region
The truncated rods were heated with several steps and the sample was characterized by an atomic force microscope (AFM) after each process
Summary
Direct laser writing (DLW) is an effective and flexible approach to inducing two-photon polymerization (2PP) in various photoresists and has been intensively studied for the fabrication of three-dimensional (3D) arbitrary micro-structures including 3D photonic crystals (PhCs) [1,2,3,4,5,6,7,8,9,10]. Though the feature size of the two-dimensional (2D) polymerized rods can be reduced down to less than 30 nm by employing pre-treatment methods [13,14,15], their poor thermal and mechanical stability [13,16,17] makes them less applicable for fabricating 3D PhCs and 3D templates of high quality [18]. These problems do not exist in all-inorganic photoresists, such as chalcogenide glasses [8]. A combination of PTT and the threshold fabrication technique leads to the stop gap of a 3D woodpile PhC that can be tuned over a large wavelength range of 318 nm from the NIR to visible region
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