Biomedical subjects
Publications and source records attributed to Sergio Calixto.
We show that it is possible to make biconvex microlenses at the end of capillary tubes. These lenses can be fixed to the flat end of photonic crystal fibers and can collimate their light.
A Raman spectroscopic study was performed to detect the surface roughness of a cadmium telluride (CdTe) wafer sample, using the 514.5, 632.8 and 830.0 nm excitations wavelengths. To verify the relation between the roughness and the structure of Raman spectra, in certain zones of the sample, we measured their roughness with an atomic force microscopy. It was found that, using the 830 nm wavelength there is a direct correspondence between the spectrum structure and the surface roughness. For the others wavelengths it was found, however, that there is not a clearly correspondence between them. Our results suggest that, using the excitation wavelength of 830 nm the Raman spectroscopy can be used as an on-line roughness monitor on the CdTe growth.
The fabrication and testing of glass microlenses with rod and spherical shapes are described. The sizes of the lenses range from tens of micrometers to several millimeters. The surfaces of the lenses were fabricated by the melting method. These surfaces have been studied by several methods. The theoretical behavior of the lenses was investigated by ray tracing. Some applications of the lenses are presented.
A technique for developing recording gratings in situ in Photoresist Shipley S-1822 is described. The developing process is accomplished by use of a spray without removing the sample from the optical setup. The results for the diffraction efficiency show that there is not a large difference between gratings achieved with the traditional wet development process and those obtained with the in situ developing technique. The potential of this in situ developing technique is shown with a moiré interferometric experimental setup used for displacement showing.
The optical response of a photopolymerizable formulation consisting of a bisphenol A epoxy acrylate oligomer, a divinyl ether, and a photoinitiator system containing Rose Bengal was studied by recording holographic gratings. This blend is sensitive to blue-green light. Single- and double-exposure volume phase holograms were recorded. In addition to these examples, surface depth measurements were made by means of a holographic contour technique.
It is shown that a relief is generated when spatial distributions of infrared light (lambda = 10.6 microm) are recorded on albumen films. The relief can be applied to the fabrication of microelements, such as diffraction gratings and microlenses. Examples are shown.
Surface-relief transmissive diffractive elements were fabricated by embossing. The master was made by lithography with a self-developing photopolymer. The highly cross-linked structure exhibited by the polymer has made possible the direct replication by thermal embossing of polyethylene substrates. Fabricated elements are meant to work with mid-infrared radiation. The influence of some process variables, related to the performance of the diffractive elements, is analyzed.
Interference gratings, plano-convex microlenses, and spherical microlenses have been made in silicone. Lenses were fabricated by the melting method. Two substrates have been tried: glass and Teflon. The latter substrate lets us fabricate low-f-number lenses. We made spherical microlenses by placing pieces of silicone near a thermal source and studied resolution of the lenses by investigating the images they gave of a test chart. We made low-spatial-frequency gratings by recording interference patterns and studied parameters involved in the recording. A study of the profile of the gratings and lenses was done with a mechanical surface analyzer.