Luis Alberto Sanchez
@cal-sens.com
Cálculo y Estructuras Sensadas S.L.
Cálculo y Estructuras Sensadas S.L.
EDUCATION
PhD in Physics
RESEARCH, TEACHING, or OTHER INTERESTS
Atomic and Molecular Physics, and Optics, Materials Science
Scopus Publications
Scopus Publications
Bryan Sanipatin, Luis A. Sánchez, Daniel Maldonado-Hurtado, Javier Madrigal, David Barrera, and Salvador Sales
Elsevier BV
Luís A. Sánchez, Martina Delgado‐Pinar, Antonio Díez, and Miguel V. Andrés
Wiley
AbstractOpto‐mechanical interactions in different photonic platforms as optical fibers and optical microresonators are raising great attention, and new exciting achievements have been reported in the last few years. Transverse acoustic mode resonances (TAMRs) in optical fibers –which can be excited optically via electrostriction and generate forward Brillouin scattering (FBS)– are being promoted as the physical mechanism for new fiber‐sensing concepts. Here, the study reports a novel approach to detect and characterize opto‐excited TAMRs of an optical fiber based on the interplay with optical surface wave resonances, i.e., optical whispering‐gallery mode (WGM) resonances. TAMRs induce perturbations in the geometry and the dielectric permittivity of the fiber over the entire cross‐section. It is shown that these perturbations couple the acoustic with the optical resonances and affect WGMs in a noticeable way. The study proposes and demonstrates the use of WGMs for probing opto‐excited TAMRs in optical fibers. This probing technique provides the narrowest linewidths ever reported for the TAMRs and demonstrates an optimum efficiency for the detection of low‐order TAMRs. The interplay between sensitivity, bandwidth, and Q factor of the WGM resonance is discussed.
Alba de las Heras, Ana I. Gómez-Varela, María-Baralida Tomás, Rosa Ana Perez-Herrera, Luis Alberto Sánchez, Francesca Gallazzi, Beatriz Santamaría Fernández, Mario Garcia-Lechuga, Maria Vinas-Pena, Martina Delgado-Pinar,et al.
MDPI AG
The COVID pandemic is forcing the renewal of scientific conferences, offering opportunities to introduce technological and inclusive developments. Our analysis focuses on the implementation of inclusive practices for female and early-career researchers in a virtual scientific conference. This organization approach was applied in the XIII Spanish Optical Meeting (RNO2021), which was also characterized by avatars interacting in an online metaverse. The effectiveness of inclusive policies and novel technological tools was evaluated using the participation data and a post-conference survey. Our study reveals the high impact of inclusive actions and a strong interest in the scientific community to explore conference advances.
Luis A. Sánchez, Martina Delgado-Pinar, Antonio Díez, and Miguel V. Andrés
IEEE
Whispering galley modes (WGM) are optical resonances that can exist in circularly symmetric dielectric resonators where the electromagnetic field is confined near to the surface of the resonator. Optical fibers are cylindrical microresonators with WGM resonances with quality factors up to 107. WGMs resonance frequencies are sensitive to perturbations in both the dimensions of the resonant cavity and to changes in the material, which has been exploited in numerous sensing and characterization applications [1]–[2]. Acoustic oscillations inside the dielectric microresonator can modify the refractive index of the material due to the elasto-optic effect and also the transverse dimensions of the resonator. Therefore, they can eventually be detected using WGMs. In this work, we take advantage of this mechanisms, and we demonstrate a novel optical technique to detect transverse acoustic mode resonances (TAMRs) in optical fibers using WGMs. TAMRs are excited by the optical beam propagating in the fiber core and are responsible for the forward Brillouin scattering effect. They feature strain components only in the transverse plane of the waveguide axis.
L. A. Sánchez, C. A. Álvarez-Ocampo, M. Delgado-Pinar, A. Díez, J. L. Cruz, and M. V. Andrés
IEEE
Opto-mechanical interactions in optical fibers based on Forward Brillouin Scattering (FBS) can lead to a new paradigm for the optical fiber sensing technology, since it allows monitor the surroundings of the fiber without requiring light interaction with the fiber outer medium. Point and distributed sensing schemes have been demonstrated based on FBS. The development of applications based on this nonlinear effect requires accurate knowledge of the properties of the acoustic modes behind FBS. In this work, different all-optical approaches for the excitation and detection of such transverse acoustic mode resonances in optical fibers will be presented and discussed.
Luis A. Sánchez, Antonio Díez Cremades, José L. Cruz, and Miguel V. Andrés
SPIE
The capabilities of optical fiber sensing based on forward Brillouin scattering (FBS) can be extended by exploiting the differential response to fiber perturbations of radial and torsional-radial acoustic modes. Radial and a subfamily of torsional-radial modes present a different sensitivity to changes of temperature and strain. By combining experimental measurements of the resonance frequencies of the different acoustic modes, we obtain (1) the Poison ratio of the optical fiber with an accuracy better than 1‰, and its temperature and strain responses, and (2), we demonstrate simultaneous and discriminative measurements of strain and temperature with accuracy better than 25 με and 0.2 °C, respectively.
Luis A. Sánchez, Antonio Díez, José Luis Cruz, and Miguel V. Andrés
MDPI AG
In-fiber opto-mechanics based on forward Brillouin scattering has received increasing attention because it enables sensing the surrounding of the optical fiber. Optical fiber transverse acoustic resonances are sensitive to both the inner properties of the optical fiber and the external medium. A particularly efficient pump and probe technique—assisted by a fiber grating—can be exploited for the development of point sensors of only a few centimeters in length. When measuring the acoustic resonances, this technique provides the narrowest reported linewidths and a signal-to-noise ratio better than 40 dB. The longitudinal and transverse acoustic velocities—normalized with the fiber radius—can be determined with a relative error lower than 10−4, exploiting the derivation of accurate asymptotic expressions for the resonant frequencies. Using this technique, the Poisson’s ratio of an optical fiber and its temperature dependence have been measured, reducing the relative error by a factor of 100 with respect to previously reported values. Using a single-point sensor, discriminative measurements of strain and temperature can be performed, achieving detection limits of ±25 με and ±0.2 °C. These results show the potential of this approach for the development of point sensors, which can be easily wavelength-multiplexed.
L.A. Sánchez, C. Cuadrado-Laborde, A. Carrascosa, A. Díez, J.L. Cruz, and M.V. Andrés
Elsevier BV
L. A. Sánchez, A. Díez, J. L. Cruz, and M. V. Andrés
Optica Publishing Group
A novel method that enables simultaneous and discriminative measurement of strain and temperature using one single optical fiber is presented. The method is based on the properties of transverse acoustic mode resonances (TAMRs) of the optical fiber. In particular, it is based on the different sensitivity to temperature and strain that exhibit the radial modes R0,m and a family of torsional-radial modes denoted as T R 2 , m ( 1 ) . We show that the resonance frequencies of both types of resonances shift linearly with temperature and strain, but at different rates. By the combined use of the different sensitivities of the two families of TAMRs, we experimentally demonstrate discriminative measurements of strain and temperature. A detection limit of strain and temperature better than 25 µε and 0.2 °C is achieved.
L. A. Sánchez, A. Díez, J. L. Cruz, and M. V. Andrés
Optica Publishing Group
Transverse acoustic mode resonances enable a high accuracy determination of Poisson’s ratio and elastic properties of optical fibers. An all-optical pump and probe technique is used for efficient excitation and accurate characterization of both, radial and torsional-radial acoustic resonances of optical fibers. Simple and precise algebraic expressions for the frequencies of high order acoustic resonances are derived, enabling a rigorous analysis of the experimental data using standard least squares fitting. Following this approach, the determination of Poisson’s ratio does not require the measurement of any physical length, but only frequency measurements are required. An accuracy better than 1 ‰ is achieved. The dependence of the fiber Poisson’s ratio with temperature is also determined experimentally.
L. A. Sanchez, A. Diez, J. L. Cruz, and M. V. Andres
IEEE
The interaction between light and sound in optical fibers is a phenomenon that researchers have been investigated for many decades. Among all the opto-acoustic effects that occurs in optical fibers, forward-stimulated Brillouin scattering (FSBS) has become of great interest as sensing mechanism due to the dependence of the excited acoustic resonances on both internal parameters [1] , [2] and surroundings [3] of the optical fiber. The vibrational modes behind FSBS are transverse acoustic resonances, in particular, the radial modes R 0m and the torsional-radial modes TR 2m . Most of the experiments reported based on FSBS exploit the properties of either the radial or the torsional-radial modes. In this work, we show that combining the characteristics of both types of resonances the possibilities of FSBS for fiber sensing can be extended further. In particular, we report the measurement of the Poisson ratio of the optical fiber with high accuracy, as well as its temperature dependence.
Miguel Guada, Ángel Moretón, Sofía Rodríguez‐Conde, Luis Alberto Sánchez, Mario Martínez, Miguel Ángel González, Juan Jiménez, Leonardo Pérez, Vicente Parra, and Oscar Martínez
Wiley
AbstractAmong the many characterization techniques for solar panel testing, two, electroluminescence (EL) and photoluminescence (PL), can provide useful visual information about the presence of different types of cell defects. EL is performed outdoors by night in commercial solar plants due to the very weak luminescence emission compared to sunlight. PL faces the added difficulty of needing to find a large‐area homogeneous light source to excite the modules. Since nighttime work poses many drawbacks and risks, a daylight outdoor EL/PL system would be useful for offering safe inspection of solar plants. We present daylight luminescence techniques based on a bias switching method, in which a pulsed luminescence signal is obtained by alternating the polarization state of the solar panels, synchronizing it with the luminescence image detection by an InGaAs camera. Fast switching and selecting an optimized exposure time are key to achieving high‐quality images. The daylight luminescence method described herein allows both EL and PL luminescence images to be obtained, even under high solar irradiance conditions.
L. A. Sánchez, A. Díez, J. L. Cruz, and M. V. Andrés
Optica Publishing Group
A new technique, to the best of our knowledge, for the characterization of the effective refractive index modulation in optical fibers due to transverse acoustic mode resonances excited by electrostriction is reported. The resonances excited by an optical pulse are probed by a narrow bandwidth long-period grating (LPG) inscribed in the fiber, which is interrogated by a continuous wave (CW) beam. The LPG used in this experiment has a narrow bandwidth and high sensitivity to small mode index perturbations, allowing the measurement of index variations from below 10 − 9 to 10 − 6 . Radial and torsional-radial acoustic modes were characterized up to 1.1 GHz. The linewidth of resonances was found to be much shorter than in previous reports in which long fiber lengths are typically required, obtaining Q factors as high as 5000.
L. A. Sánchez, A. Moretón, M. Guada, S. Rodríguez-Conde, O. Martínez, M. A. González, and J. Jiménez
Springer Science and Business Media LLC
L. A. Sánchez, A. Moretón, M. Guada, S. Rodríguez-Conde, O. Martínez, and J. Jiménez
Springer Science and Business Media LLC
Upgraded metallurgical-grade silicon (UMG Si) solar cells with different ranges of efficiencies were characterized through electroluminescence imaging (ELi) and light-beam induced current (LBIC) measurements. The results showed a good correlation between the EL intensity and the efficiency of the solar cells. ELi images gave a bright contrast at the defects, grain boundaries and intragrain defects, and dark contrast inside the grain bodies. Metallic impurities are much more present in some cells due to the directional solidification of the Si ingot. Local short-circuit current mapping with LBIC measurements revealed a bright zone in the neighborhoods of the defects due to the depletion of impurities. Internal quantum efficiencies (IQE) and effective diffusion lengths (L_eff) were calculated using different excitation wavelengths. High resolution LBIC measurements revealed micrometric clusters of impurities around intragrain defects.