Silica-based diffractive/refractive hybrid microlenses fabricated by multiphoton lithography

H. Nishiyama; M. Mizoshiri; J. Nishii; Y. Hirata

doi:10.1117/12.795014

25 August 2008 Silica-based diffractive/refractive hybrid microlenses fabricated by multiphoton lithography

H. Nishiyama, M. Mizoshiri, J. Nishii, Y. Hirata

Proceedings Volume 7056, Photonic Fiber and Crystal Devices: Advances in Materials and Innovations in Device Applications II; 70561F (2008) https://doi.org/10.1117/12.795014
Event: Photonic Devices + Applications, 2008, San Diego, California, United States

Abstract

SiO₂-based diffractive/refractive hybrid microlenses were fabricated by using femtosecond laser-induced nonlinear optical processes. Recently, hybrid devices have received much attention as important components for optical pickup systems and integrated sensors. SiO₂-based devices are particularly promising because of high transparency, physical and chemical stabilities. For these devices, microfabrication upon nonplanar substrates such as convex lenses, which is difficult for the semiconductor processes, is required. In this study, microFresnel lens patterns were directly written inside positive-tone resists upon convex microlenses of 240 μm diameters by using femtosecond laser-induced nonlinear absorption. The spot diameters are primarily determined at any position inside the resist by the region volume at which the nonlinear absorption occurs. Therefore, the precise patterns could be formed even upon the nonplanar substrates. After post-exposure-bake and development treatment, the patterns were transferred onto underlying lenses by CHF₃ plasma. Here, the etching depth was 1 μm. Consequently, SiO₂-based hybrid lenses with smooth surfaces were obtained. When He-Ne laser of 632.8 nm wavelength was coupled to this hybrid lens, the focal spot was 630 μm from the lens surfaces. This focal length agreed with theoretical value of 618 μm. More functional optical devices would be realized by improvement of fabrication processes.

Citation Download Citation

H. Nishiyama, M. Mizoshiri, J. Nishii, and Y. Hirata "Silica-based diffractive/refractive hybrid microlenses fabricated by multiphoton lithography", Proc. SPIE 7056, Photonic Fiber and Crystal Devices: Advances in Materials and Innovations in Device Applications II, 70561F (25 August 2008); https://doi.org/10.1117/12.795014

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