Fabrication and Characterization of Multi-Scale Micro Lens Arrays with Anti-reflection and Diffusion Properties
Date Issued
2010
Date
2010
Author(s)
Lee, Chih-Hsien
Abstract
It has been reported that two dimensional taper-shaped sub-wavelength periodic structures could reduce the reflectivity at the interface of different materials effectively. Though this technique is not widely used to replace traditional thin film coating presently, it is expected to become a more suitable solution when applied to ever smaller optical elements. It has been pointed out that compound eyes of flies have the ability to enhance both viewing angle and to increase light extraction efficiency simultaneously. Therefore, we expect such a compound integration of micro and nano structures can have the potential to become a multi-function optical element and will be applied in LCD and LED light extraction industries.
In this thesis, we would utilize two-beam interference lithography to define the sub-wavelength structures (SWS), and use the mechanism of reducing etching mask to easily fabricate taper-shaped SWS on a SiO2 substrate in a reactive ion etching (RIE) system. In addition, we would fabricate micro structures on a Si substrate by utilizing photolithography and inductive couple plasma (ICP) etching. After that, we would use these two-scale micro/nano molds to fabricate compound eye structures on a flexible substrate. Then we transferred SWS from the flat surfaces to the curved surfaces of micro lens arrays by combining nanoimprint and hot-extrusion technique. Thus it is a very simple and reproducible method to fabricate artificial compound eye structures. Furthermore, we would measure the reflectivity of a single micro lens to confirm the effect of anti-reflection by utilizing our homemade reflectometer.
Finally, we would transfer the compound structures from the flexible substrate to the millimeter hemisphere of an LGP by utilizing hot-embossing process. Then we would measure the transmittance and diffusibility of an LGP with compound structures by utilizing a CCD camera and an integrating sphere, respectively. The measurement results show that the multi-function optical element has potential to be applied in back light units.
Subjects
Sub-wavelength structure
micro lens arrays
compound eye
nanoimprint
interference lithography
Type
thesis
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