Sergio Calixto - Academia.edu (original) (raw)

Papers by Sergio Calixto

Fabrication of the relief focusing elements are known to include the illumination of light sensit... more Fabrication of the relief focusing elements are known to include the illumination of light sensitive materials through computer generated /l/ multy-grey-level amplitude mask with corresponding amplitude function of the focusing element /2,3/. In this report the use of dry photopolymer films (see /4/) is discussed. The photopolymer films based on the acrylamide (monomer), polyvinylalcohol (binder), methylene blue (sensitizer) and triethanolamine (initiator) were prepared according to the procedure previously described /4/. The exposure set up used is shown on the fig.1. The photosensitive layer provided sensitivity in the 600-700 nm spectral region, so as a light source 1 the 3 00 Watt halogen lamp with the reflector 2 was used. The filter 3 absorbed the heat radiation to prevent the amplitude mask damaging. The parallel beam at the output was formed by lenses 4. Polymer layer 7 was placed on the glass substrate 8. The direct contact of polymer layer and amplitude mask 6 was provided by glass substrate 5. Polymer layer thickness was 100 μm.

Proceedings of SPIE, Jun 21, 2004

Polarization holographic gratings with surface relief in azobenzene-containing polymers. [Proceed... more Polarization holographic gratings with surface relief in azobenzene-containing polymers. [Proceedings of SPIE 5449, 24 (2004)]. Ivanka Mancheva, Geminiano Martinez-Ponce, Sergio Calixto, Tsveta Petrova, Natalia Tomova, Violeta Dragostinova, Ludmila Nikolova. Abstract. ...

Laser Physics, 2004

Abstract—Silica holey fibers with a core surrounded by a few rings of air holes of a large diamet... more Abstract—Silica holey fibers with a core surrounded by a few rings of air holes of a large diameter and pitched by a large spacing are fabricated and characterized in terms of their linear-optical properties (ie, light-delivering quality and optical losses). An optimal value of the relative hole diameter, 0.52±0.05, is found, which provides a single-mode propagation of the launched laser beam along the fibers in the visible (wavelength 633 nm) and near IR (wavelengths 1310 and 1550 nm) spectral ranges with low (about 10–30 dB/km) ...

Revista Mexicana De Fisica, Aug 15, 2011

Optical science and engineering, May 31, 2001

Journal of the Optical Society of America, 1977

Journal of Luminescence, 2021

$Research paper thumbnail of Liquid refractive index measured through a refractometer based on diffraction gratings$

Optics Express, 2019

We developed two versions of refractometers to measure the refractive index of liquids. One refra... more We developed two versions of refractometers to measure the refractive index of liquids. One refractometer comprises a glass cell with a surface relief grating on the inner face of one of its walls, while the other one is a microfluidic channel in the form of serpentine that behaves as a grating. Measurements of the liquid refractive index were performed by sensing the first order intensity. Several liquids have been used including an organic one. Calibration plots are shown.

$Research paper thumbnail of A refractometer based on a sinusoidal grating$

SPIE Proceedings, 2016

Here we present a refractometer for liquids based on a sinusoidal relief grating immersed in a sm... more Here we present a refractometer for liquids based on a sinusoidal relief grating immersed in a small cuvette. He – Ne light is sent to the cuvette + grating device where it is diffracted. Zero, +1 and -1 orders appear. It is possible to calibrate the device by measuring +1 order intensity, when different liquids with known refractive index are poured in the cuvette. A theoretical study has been developed that supports the experimental results.

Frontiers in Optics, 2003

The field of optofluidics as such emerged in the year 2000. It integrates principles and concepts... more The field of optofluidics as such emerged in the year 2000. It integrates principles and concepts of optics and microfluidics. Optofluidic devices are hollow components where, until now, just isotropic liquids with different properties have been used. This process makes the optofluidic component a tunable device. Optofluidic components include lenses, prisms and diffraction gratings, among others. The structure of an optofluidic grating consists of a long and thin serpentine microchannel where liquids are injected. Recently, we demonstrated that using isotropic liquids in an optofluidic grating enables it to be used as a refractometer. Here, we present the results when liquids showing an optical activity are injected in the optofluidic grating making it tunable. With this change now the gratings respond different to polarized light and thus are called polarization gratings. Some liquids with optical activity have been tested. Among them a liquid that consists of a mixture of penicillin and water has been used. Penicillin has a high Specific Rotation, [α]D20= +290o+5o (2% in H2O). The fabricated grating microchannels had a square profile, with dimensions of 200 µm width, 500 µm depth and 5 mm length. The distance between the microchannels is 200 µm. The illuminating light had various wavelengths (632.8 nm, 543 nm and 468 nm) and polarization states such as linear, elliptical and circular. The states of polarization and diffraction efficiency of the first diffracted order, under the illuminating parameters, were studied.

Materials, 2019

The use of electronic devices to measure Relative Humidity (RH) is widespread. However, under cer... more The use of electronic devices to measure Relative Humidity (RH) is widespread. However, under certain circumstances, for example when explosive gases are present, a spark-free method should be used. Here we suggest the use of stimuli-responsive materials, like gelatin and interpenetrated polymers, to detect RH with an optical method. These materials are hydrophilic. When water vapor is absorbed by the films the molecules attach to the films molecular network. The result is that the film thickness increases and their refractive index changes. To detect the change of these two parameters an optical method based on diffraction gratings is employed. Surface diffraction gratings are recorded on the films. Then gratings are placed in an optical configuration that is immersed in a climatic chamber. A light beam is sent to the grating where it is diffracted. Several light orders appear. Due to the absorption of water molecules the films swell and grating surface modulation changes. This imp...

Journal of the Optical Society of America, Mar 16, 2012