This article describes the fabrication of MgF₂ and MgO thin-film-based optical filters and compares the optical transmission of the filters over UV. The MgF₂ thin-films were deposited by use of an e-beam technique and their optical properties were characterised by ellipsometry. The effect of substrate temperature on the optical properties was studied. The MgF₂ optimum refractive indices were obtained with a substrate temperature between 200 °C and 300 °C. Optical simulations were performed to compare the performance of MgF₂ and MgO in the fabrication of near-UV narrow bandpass optical filters. While MgO-based optical filters result in a higher transmittance peak intensity, especially at 350 nm, the MgF₂ optical filters are narrower, present lower values of FWHM, a mean value of 20 nm. This feature could be especially relevant for specific applications on fluorescent optical sensors. Finally, a Fabry-Perot based on a MgF₂/TiO₂ optical filter was deposited, using an e-beam technique for the MgF₂ thin-films and RF-sputtering technique for the TiO₂ thin-films. The MgF₂/TiO₂ optical filter peak transmittance is approximately 70% close to 400 nm, as expected. The results are discussed with focus on applications in fluorescent optical sensors for peaks at 350, 370, 380 and 400 nm, respectively.

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This paper presents the results of in vitro photodynamic therapy assays on RKO and HCT-15 cell lines. The envisaged implementation is in autonomous medical microdevices, such as endoscopic capsules for clinical treatment of several types of gastrointestinal tract tumors. Because of their very limited device volume, light fluence and fluence rate needed to destroy tumor cells should be minimized. Foscan or meta-tetra(hydroxyphenyl)chlorin (mTHPC) is used as a photosensitizer. The experimental results show that a small amount of mTHPC (0.15 mg/kg) and light fluence (5-20 J/cm²) is sufficient to obtain significant photodynamic activity. An array of LEDs with peak transmittance at 652 nm is used as a portable light source for the maximum quantum efficiency in producing singlet oxygen. Irradiation to a light fluence between 2.5 and 10 J/cm² is achieved by an increased exposure time at an 11 mW/cm² light fluence rate, while mTHPC concentrations of 0.5, 1, 5, and 10 μg/mL are used. The experimental results show that decreased cell viability (down to 30%) can be obtained for 1-5 μg/mL of mTHPC concentrations and 2.5 J/cm² of light fluence. Such light fluence and light fluence rate are compatible with the endoscopic capsules batteries.

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This paper reports on the development of a technology for the wafer-level fabrication of an optical Michelson interferometer, which is an essential component in a micro opto-electromechanical system (MOEMS) for a miniaturized optical coherence tomography (OCT) system. The MOEMS consists on a titanium dioxide/silicon dioxide dielectric beam splitter and chromium/gold micro-mirrors. These optical components are deposited on 45° tilted surfaces to allow the horizontal/vertical separation of the incident beam in the final micro-integrated system. The fabrication process consists of 45° saw dicing of a glass substrate and the subsequent deposition of dielectric multilayers and metal layers. The 45° saw dicing is fully characterized in this paper, which also includes an analysis of the roughness. The optimum process results in surfaces with a roughness of 19.76 nm (rms). The actual saw dicing process for a high-quality final surface results as a compromise between the dicing blade's grit size (#1200) and the cutting speed (0.3 mm s−1). The proposed wafer-level fabrication allows rapid and low-cost processing, high compactness and the possibility of wafer-level alignment/assembly with other optical micro components for OCT integrated imaging.@en

The wafer-level fabrication of a Michelson interferometer using optical MEMS technologies is presented. The intended application is in Optical Coherence Tomography (OCT). The micro fabrication involves two steps: the 45° saw dicing of glass substrate and the subsequent deposition of a dielectric multilayer and metallic layers to obtain a beam splitter and waveguide micro mirrors, respectively. The Michelson interferometer was designed for use in the near-infrared range of 800–900 nm. A 50/50 non-polarized beam splitter was obtained with only four layers (using titanium dioxide and silicon dioxide). The micro mirrors for the required spectral range were fabricated by sputtering of chromium and gold layers. The dicing cuts, which were performed with a custom-made 45° dicing blade, resulted in smooth slopes. The surface’s roughness is 19.76 nm at setting and can be reduced to approximately 50% with a soft additional dicing cut. The height of the 45° surfaces was approximately 400 μm, which is in accordance with the design. The micro Michelson interferometer can be easily integrated with other optical components into a complete OCT miniaturized system.@en