Microlens arrays of high-refractive-index glass fabricated by femtosecond laser lithography |
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Authors: | Hiroaki Nishiyama Junji Nishii Yoshinori Hirata |
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Affiliation: | a Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871, Japan b National Institute of Advanced Industrial Science and Technology, 1-8-31 Midorigaoka, Ikeda, Osaka 563-8577, Japan |
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Abstract: | Microlens arrays of high-refractive-index glass GeO2-SiO2 were fabricated by femtosecond laser lithography assisted micromachining. GeO2-SiO2 thin glass films, which were deposited by plasma-enhanced chemical vapor deposition, have a refractive index of 1.4902 and exhibit high transparency at wavelengths longer than 320 nm. Using a femtosecond laser, three-dimensional patterns were written inside resists on GeO2-SiO2 films, and then the patterns were transferred to the underlying films by CHF3 and O2 plasma treatments. This combined process enabled us to obtain uniform microlens structures with a diameter of 38 μm. The heights of the transferred lenses were approximately one-quarter the height of the resist patterns, due to differences in the plasma etching rates between GeO2-SiO2 and the resist. The lens surfaces were smooth. When 632.8-nm-wavelength He-Ne laser light was normally coupled to the lenses, focal spots with a diameter of 3.0 μm were uniformly observed. The combined process was effective in fabricating three-dimensional surfaces of inorganic optical materials. |
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Keywords: | 42 62 Cf 42 82 Cr |
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