The study on spatial resolution in two-photon induced polymerization
The study on spatial resolution in two-photon induced polymerization
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DOI：
10.1117/12.645221
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发表时间：
2006-01
期刊：
影响因子：
--
通讯作者：
K. Takada;Hongbo Sun;S. Kawata
中科院分区：
文献类型：
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作者：
K. Takada;Hongbo Sun;S. Kawata
我们以前已经证明，双光子诱导聚合可以制造出空间分辨率约为120 nm的光子晶体和微机械等复杂的三维结构。在这份报告中，我们展示了分辨率提高到65 nm。实验上，利用大数值孔径物镜将780 nm的飞秒激光脉冲聚焦到可光聚合树脂中。该树脂是通过自由基引发聚合的。在自由基聚合中，溶解在树脂中的氧分子通过清除引发聚合的自由基来抑制聚合反应。在控制激光脉冲能量的情况下，自由基只有在曝光能量大于聚合阈值的区域才能存活并引发聚合，从而导致亚衍射限制的空间分辨率。为了进一步提高制备精度，我们在树脂中引入了自由基猝灭剂，在最佳浓度下，横向空间分辨率提高到100 nm。此外，我们通过控制光纤内的曝光剂量，制作了连接在两个锚之间的悬浮光纤。在用乙醇除去未固化的树脂并干燥后，得到了65 nm宽的纤维，这表明可能具有类似尺寸的空间分辨率。尺寸小于1/10的激发波长可以满足许多光电子器件的要求。
We have previously demonstrated that two-photon induced polymerization allows fabrication of complex threedimensional structures such as photonic crystals and micromachines with a spatial resolution around 120 nm. In this report, we show the resolution improvement till 65 nm. Experimentally, 780-nm femtosecond laser pulses were focused into a photopolymerizable resin by a high numerical aperture objective lens. The resin is polymerized by means of radical initiation. In the radical polymerization, oxygen molecules dissolved in the resin inhibit the polymerization reactions by scavenging the radicals that initiate the polymerization. At controlled laser pulse energy, the radicals can survive and initiate polymerization only at the region where exposure energy is larger than the polymerization threshold, leading to a sub-diffraction-limited spatial resolution. In order to further improve the fabrication accuracy, we introduced a radical quencher into the resin, and at an optimized concentration the lateral spatial resolution was improved to 100 nm. Moreover, we fabricated a suspended fiber connected between two anchors by controlling the exposure dose within the fiber. After removing the unsolidified resin by ethanol and drying, a 65-nm width fiber was obtained, suggesting a possible spatial resolution of similar dimension. The size less than 1/10 of the excitation wavelength could satisfy requirements of many photonic and optoelectronic devices.