This paper proposes a novel method for integrating inclined mirrors with precise angles and smooth surfaces in on-chip Fresnel lens optical pick-up-head applications. A glycerol-compensated inclined-exposure technology was adopted for 45° mirror pair fabrication. This technology can fabricate 19–90° inclined structures onto SU-8 negative tone resist with thickness from 100 to 1000 µm. Glycerol is employed as an index matching material during exposure to compensate for the refractive index difference between the air and SU8, thus extending the possible inclined angles from 54° (in air) down to 19° (in glycerol). To eliminate reflected induced patterns, CK-6020L resist is employed as an antireflection layer. The surface roughness, measured by AFM, is below 7 nm for various inclined angles. Device fabrication has been successfully completed and test results demonstrated a functional VCSEL (vertical cavity surface emitting laser) beam focusing on a 5 µm spot. Further beam size reduction into the sub-micrometer range requires an objective lens with high numerical aperture, which is not within the scope of this paper. The fabricated optical components are robust and accurately aligned. This new integrated approach provides an easy and low-cost fabrication method for optical pick-up heads eliminating the need for manual assembly.
The purpose of this study was to characterize the etching mechanism, namely, the etching rate and the activation energy, of a titanium dental implant in concentrated acid and to construct the relation between the activation energy and the nanoscale surface topographies. A commercially-pure titanium (CP Ti) and Ti-6Al-4V ELI surface were tested by shot blasting (pressure, grain size, blasting distance, blasting angle, and time) and acid etching to study its topographical, weight loss, surface roughness, and activation energy. An Arrhenius equation was applied to derive the activation energy for the dissolution of CP Ti/Ti-6Al-4V ELI in sulfuric acid (H2SO4) and hydrochloric acid (HCl) at different temperatures. In addition, white-light interferometry was applied to measure the surface nanomorphology of the implant to obtain 2D or 3D roughness parameters (Sa, Sq, and St). The nanopore size that formed after etching was approximately 100–500 nm. The surface roughness of CP Ti and Ti-6Al-4V ELI decreased as the activation energy decreased but weight loss increased. Ti-6Al-4V ELI has a higher level of activation energy than Ti in HCl, which results in lower surface roughness after acid etching. This study also indicates that etching using a concentrated hydrochloric acid provided superior surface modification effects in titanium compared with H2SO4.
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