Photopolymerization and Metalization for Fabricating Functional Devices and Metamaterials
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0921-T02-01
Photopolymerization and Metalization for Fabricating Functional Devices and Metamaterials Satoshi Kawata1, Takuo Tanaka1, Nobuyuki Takeyasu1, and Sana Nakanishi2 1
Nanophotonics Lab., RIKEN, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan
2
Applied Physics, Osaka University, Yamadaoka 2-1, Suita, Osaka, 565-0871, Japan
ABSTRACT Two-photon-induced photopolymerization is useful for fabricating 3D micro/nano-structures with the resolution of the sub-diffraction limit. By using this method, photonic crystal was created with pre-compensation of shrinkage of photopolymer. On the contrary, the shrinkage was utilized to reduce the structure size. A micro-lens array was used to produce a mass of structures in parallel. Furthermore, metallization of the 3D polymer templates was conducted by electroless metal plating. These fabrication techniques are applicable to functional micro/nano devices. INTRODUCTION We present two-photon-induced photopolymerization for fabricating 3D micro/nano-structures [1, 2]. In this method, arbitrary three-dimensional polymer structures are fabricated by scanning tightly focused infrared femto-second laser in three dimensions. Recently, we extended this technique to fabricate functional micro devices including photonic band-gap crystals [3] and movable micro-springs. The shrinkage of polymer during polymerization is utilized to reduce the structure size beyond the diffraction limit of light [4]. A micro-lens array is used to produce a mass of structures in parallel [5]. In this presentation, metalization of fabricated polymer structures will also be described. We coat metal on the surface of polymer by electroless metal plating, but not on the glass substrate [6, 7, 8]. These fabrication techniques are useful for metallic metamaterials exhibiting negative refraction. In the presentation, we would like to show our design of the structure [9]. In the end, we talk about our newly invented diffraction-free imaging with nano metal rod array [10]. EXPERIMENTAL DETAILS AND DISCUSSIONS Pre-compensation Most efforts in fabricating PhCs using two-photon photopolymerization are frustrated by the suffering of no band gap effect observed in laser-written structures except for limited examples [11-14]. Here we report a solution to the addressed problem by adopting a fabrication scheme that takes full advantage of arbitrary 3D laser prototyping, by the adopted approach enables precise pre-compensation to the structure deformation arising from liquid-solid phase transformation accompanied with photopolymerization, an issue has to be solved in polymer PhCs. Figure 1 illustrates the logpile structure. For the purpose of diagnosis and comparison, a similar lattice was employed in this research.
Figure 1. Schematic logpile PhC structure
Figure 2. Precompensation of logpile PhCs. All structures were designed with horizontal cross section of 20 µm 20 µm (a) No precompensation, PhC top area shrunk to 17 µm 17 µm. (c) A nearly cubic PhC structure after precompensation according to calculated deformation.
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