Design, fabrication, and characterization of a multidimensional prism.

In this research, a novel multidimensional prism with three distinct 45°, 135°, and 225° inclined optical surfaces were realized by using inclined exposure technology and SU-8 polymer. To obtain a smooth surface, the solvent loss percentage and temperature of post-exposure bake (PEB) are two key factors that need to be well controlled during fabrication. The experimental results showed that surface roughness can achieve 42.9±7.6 nm, which is one-tenth of high-precision machining or molding processes, under the processes parameter combinations of PEB temperature, and solvent loss percentage is 95°C and 82.86%, respectively. The surface reflectivity of the prism was measured by using a He-Ne laser, and reflectivity of the prism surface without and with aluminum metal film was 90.8% and 91.8%, respectively. The slight difference of reflectivity means that a prism with a high-quality inclined surface can be realized. The functionality of the prism for three lasers was also verified with RGB lasers, and it successfully demonstrated the feasibility of application of a multidimensional prism on the optical system. Finally, the utilization of inclined exposure technology not only monolithically integrates three 45° inclined surfaces into one prism without precision assembly but also greatly simplifies the fabrication processes to further reduce the cost. This component and technology can also be applied to medical endoscope systems if the SU-8 is replaced by PDMS or other biocompatible materials using a molding process. These results provide the potential for mass manufacturing, which is of considerable value to the optical markets.

The Effects of Acid Etching on the Nanomorphological Surface Characteristics and Activation Energy of Titanium Medical Materials.

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.

Design and fabrication of a novel prism for micro-optical system.

This study presents a special k-type (45°, 135°) microprism structure design for the lateral-type semiconductor laser of optical systems. This study combines front- and back-side inclined exposure technology to develop a k-type microprism structure and replaces the optical prism manufactured through traditional machine processing or injection molding with a new polymer (thick-film negative photoresists) micro-optical prism structure. To obtain the optimal structural surface roughness (12-15 nm at 400 µm×400 µm area), the percentage of polymer material loss caused by the solvent was controlled. This roughness level meets Blu-ray specifications (λ/10, λ=405 nm).

Design and fabrication of a copolymer aspheric bi-convex lens utilizing thermal energy and electrostatic force in a dynamic fluidic.

The purpose of this paper is to use thermal energy and electrostatic force as an alternative to high-cost precision cutting or traditional injection molding in the fabrication of COC (cyclo-olefin copolymer) plastic aspheric bi-convex lenses with high Blu-Ray transmittance (92% at 405 nm). A glass substrate was used, and ultrasonic drilling defined the clear aperture of the aspheric bi-convex lens. The copolymer lens material was measured, filled and melted into the hole. A gradient electrical potential was applied between the top and bottom electrodes of the COC liquid droplet to control the profile of the lens. The thermal energy melted the COC into a dynamic fluid, and the electrostatic force controlled the aspheric morphology of the designed profile. The resulting lenses have a clear aperture of approximately 1.14 mm and a front focal length of 4.97 mm, and the spot size of the fabricated aspheric bi-convex lenses can be controlled to approximately 0.588 microm. This technology is capable of fabricating lenses for application in micro-optical systems.

Application of the surface free energy minimization principle to modify the indentation of a polymer mirror structure.

This paper successfully used inclined exposure technology to fabricate 45 degrees polymer optical grade micromirrors (approximately 1.4 mm thick) while applying the surface free energy minimization principle to improve sidewall indentation. This paper tests the effect of the reflow process on the surface roughness of inclined surfaces. Experimental results are considered in light of the theory of minimizing free energy. The smallest surface roughness achieved in the experiments using SU-8 material with a thickness of 1.4 mm was less than 20 nm. The effect of the reflow process on the surface indentation of inclined microstructures showed that the 1D WYKO profile of maximum height fell from 0.81 microm to 0.08 microm (R(t)), which is an improvement of 90% after the reflow process. This type of micromirror can be used as a key component in Blu-Ray optical pickup heads used in portable, high-density storage systems.