Victor Ulises Lev Contreras Loera | Universidad Nacional Autónoma de México (original) (raw)
Papers by Victor Ulises Lev Contreras Loera
Airborne acoustic trapping by ultrasonic phased arrays has seen great advances in recent years, a... more Airborne acoustic trapping by ultrasonic phased arrays has seen great advances in recent years, and yet the manipulation of objects with different shapes and sizes or heavy particles remains challenging. Here, we demonstrate that the manipulation capabilities of a standing-wave acoustic levitator can be extended by introducing intracavity high-order transverse (HOT) modes in the azimuthal direction, enabling the simultaneous trapping of several objects within a wide range of shapes and sizes with positional and rotational stability, including objects with sizes larger than one wavelength and weights in the scale of millinewtons. The conditions to generate different HOT modes are theoretically analyzed and experimentally implemented. We numerically calculate the pressure distributions, exhibiting good qualitative agreement with the experimental pressure distributions obtained with schlieren images. In addition, we calculate the acoustic force field for several examples of HOT modes and different particle sizes, which leads to a qualitative understanding of the experimental observations.
Enhanced standing-wave acoustic levitation using high-order transverse modes in phased array ultrasonic cavities, 2024
Airborne acoustic trapping by ultrasonic phased arrays has seen great advances in recent years, a... more Airborne acoustic trapping by ultrasonic phased arrays has seen great advances in recent years, and yet the manipulation of objects with different shapes and sizes or heavy particles remains challenging. Here, we demonstrate that the manipulation capabilities of a standing-wave acoustic levitator can be extended by introducing intracavity high-order transverse (HOT) modes in the azimuthal direction, enabling the simultaneous trapping of several objects within a wide range of shapes and sizes with positional and rotational stability, including objects with sizes larger than one wavelength and weights in the scale of millinewtons. The conditions to generate different HOT modes are theoretically analyzed and experimentally implemented. We numerically calculate the pressure distributions, exhibiting good qualitative agreement with the experimental pressure distributions obtained with schlieren images. In addition, we calculate the acoustic force field for several examples of HOT modes and different particle sizes, which leads to a qualitative understanding of the experimental observations.
Optics letters, Jan 15, 2018
Laser-induced breakdown spectroscopy is presented for trace element detection of liquid samples b... more Laser-induced breakdown spectroscopy is presented for trace element detection of liquid samples by analyzing a single droplet levitated by ultrasonic waves. A single liquid droplet is placed in the node of a standing acoustic wave produced by a uniaxial levitator for further chemical analysis. The acoustic levitator consists of a commercial Langevin-type transducer, attached to a concave mechanical amplifier, and a concave reflector. A micro-syringe was used to manually place individual liquid droplet samples in the acoustic levitation system. For chemical analysis, a laser-induced plasma is produced by focusing a single laser pulse on the levitated water droplet after it partially dries. The performance of the acoustic levitator on micron-sized droplets is discussed, and the detection of Ba, Cd, Hg, and Pb at parts per million (milligrams/liter) and sub-parts per million levels is reported. The process, starting from placing the sample in the acoustic levitator and ending on the ch...
Optics letters, 2017
Self-mixing interferometry (SMI) represents a robust, self-aligned technique for metrology applic... more Self-mixing interferometry (SMI) represents a robust, self-aligned technique for metrology applications. Recently, it has been shown that the detection of the frequency-modulated (FM) signal enhances the conventional SMI signal based on the amplitude modulation. Here, an all-optical, simple and effective alternative approach to detect the FM self-mixing signal is presented. We demonstrate the enhanced self-mixing approach using a laser diode emitting at 405 nm and a volume Bragg grating (VBG) to map frequency to intensity modulations for further optical detection. Our approach overcomes the spectral range limitation of the edge filtering approach based on molecular absorption filters, since the VBGs can be fabricated at any spectral range.
Nova Scientia, 2014
A través de una técnica óptica de espectroscopia basada en la absorción de luz en el rango UV vis... more A través de una técnica óptica de espectroscopia basada en la absorción de luz en el rango UV visible y un análisis estadístico multivariable es posible identificar marcas de tequila para la protección de marca in situ. Se adquirieron 40 muestras de tequilas tipo reposado de 4 marcas registradas en tiendas de licores y en algunos bares en las ciudades de León Gto. y de Zacatecas, Zac. con el propósito de encontrar similitudes y diferencias que permitan una agrupación y una posible predicción de marcas para futuras muestras. Se describe el método para la discriminación de estas bebidas alcohólicas el cual es complementario a los métodos actuales basados en análisis químicos que son mayor coste y complejidad. Los resultados muestran una buena agrupación de las marcas analizadas por lo que una nueva muestra pudiera clasificarse si pertenece o no a alguna de las marcas estudiadas. El análisis de muestras se realiza en tiempos de minutos y pueden realizarse in situ.
Optics express, Jan 18, 2016
A laser Doppler velocimetry (LDV) sensor using the edge-filter enhanced self-mixing interferometr... more A laser Doppler velocimetry (LDV) sensor using the edge-filter enhanced self-mixing interferometry (ESMI) is presented based on speed measurements of single microparticles. The ESMI detection utilizes an acetylene edge-filter that maps the frequency modulation of a semiconductor laser into an intensity modulation as the laser wavelength is tuned to the steep edge of the absorption profile. In this work, the ESMI signal was analyzed for aerosol particles of different sizes from 1 μm to 10 μm at a distance of 2.5 m. At this operation range, the signal from single particles of all sizes was successfully acquired enabling particle velocity measurements through the Doppler shifted frequency along the beam axis. For the particular case of 10 μm particles, single aerosol particles were still detected at an unprecedented range of 10 m. A theoretical treatment describing the relation between Mie scattering theory and the self-mixing phenomenon on single-particle detection is presented suppor...
Optics Letters, 2015
Self-mixing interferometry (SMI) represents a simple, robust, and self-aligned technique for metr... more Self-mixing interferometry (SMI) represents a simple, robust, and self-aligned technique for metrology applications. Still, its applicability on diffuse targets is limited to distances up to few meters. We present an enhanced approach based on the detection of the frequency-modulated (FM) self-mixing signal. The FM signal detection is achieved using an acetylene edge filter that maps laser frequency variations into intensity variations as the laser wavelength is tuned to the edge of the steep absorption profile. An experimental comparison between the enhanced and the conventional SMI approach is presented. The new approach yields to about two orders of magnitude larger signal-to-noise ratio and extends the applicability of SMI into new fields allowing longer detection ranges and lower backscattering signals.
Optics Letters, 2012
The use of double-pulse laser-induced breakdown spectroscopy (DP-LIBS) in quantitative analysis g... more The use of double-pulse laser-induced breakdown spectroscopy (DP-LIBS) in quantitative analysis generally depends on standards and calibration curves. To our knowledge, in this Letter, we report the first quantitative analysis based on DP-LIBS at low ablative energies with a self-calibrated method. We compare the effects of plasmas on the calibration-free LIBS technique, generated by DP-LIBS, and the traditional single-pulse (SP) LIBS on a steel sample. Our analyses reveal that when SP-LIBS and DP-LIBS reach comparable emission line intensities, plasma parameters and quantitative analysis are practically the same for both experiments. Additionally, we report the behavior of the emission enhancement of some elements (Fe and Cr) at low ablative pulse energies (0.2-8 mJ) using the orthogonal reheating DP-LIBS configuration.
Food Research International, 2010
Based on UV-VIS spectroscopy and chemometric techniques, a screening method is presented with whi... more Based on UV-VIS spectroscopy and chemometric techniques, a screening method is presented with which the studied brands of white and rested tequila can be differentiated among them and on the other hand, adulterate and fake tequilas can be distinguished from the corresponding genuine brands. Eighty bottles of tequila (39 white type and 41 rested type) were studied and purchased at liquor stores; special care was taken to get different batches. Through the use of support vector machine (SVM), principal component analysis (PCA) and linear discriminant analysis (LDA) the studied tequilas were differentiated and classified into 8 sets: 4 sets of white and 4 of rested tequilas; each set corresponded to a specific tequila brand. Seven additional samples with similar labeling than the 80 samples were used to validate the method and it was found that each sample was located within the ellipse of confidence of the corresponding tequila brand. Furthermore, 14 adulterated samples were generated from 2 bottles of tequila, one white and one rested, and they could be distinguishable from the genuine tequila, i.e., they were outside of the corresponding ellipse of confidence. In addition, the screening method here presented was employed to analyze rested tequilas that were purchased on the street market, i.e., fake tequilas, with the same label than 3 of the used brands in this work. These samples were discriminated from the corresponding genuine tequila brand. The results suggested that the reported method could play an important role when a quick, trustworthy and feasible result on site is needed since the test of the spirit takes minutes, affording robustness, reliability and in addition, a skilled worker is not required necessarily to apply the method.
IEEE Photonics Technology Letters, 2018
We present a simple and straightforward method to determine the phase shift between the amplitude... more We present a simple and straightforward method to determine the phase shift between the amplitude modulation (AM) and the frequency modulation (FM) of a laser diode. The approach is based on the measurement of AM and FM signals produced by the dynamical response of a laser diode exposed to weak optical feedback. The AM signal is measured directly on a photodiode detecting the emitted power and the FM signal is demodulated to intensity modulation through the edge filtering techniques using (a) a volumetric Bragg grating or (b) a Mach-Zehnder interferometer as filters prior to the signal detection. In this work, we show experimentally that the phase shift determination unveils the linewidth enhancement factor of semiconductor lasers as predicted by the Lang and Kobayashi theory.
Review of Scientific Instruments, 2021
Acoustic levitation uses focused high-intensity airborne ultrasound to hold particles in mid-air.... more Acoustic levitation uses focused high-intensity airborne ultrasound to hold particles in mid-air. It is becoming an important tool for experiments in spectrometry, lab-on-a-droplet, and display technologies. Nowadays, arrays of multiple small transducers can be used to build acoustic levitators; however, their performance depends on the optimal alignment. This work describes a simple method capable of visualizing a 2D projection of the acoustic field in real time using rainbow schlieren deflectometry. Good agreement was found between the images obtained with this technique and simulations of the acoustic pressure. It was also found that the maximum amplitudes of the field were obtained with the levitator aligned so that the power consumption was minimum, showing another simple and affordable way to adjust the levitators. As a result of the alignment optimization, it was possible for the first time to levitate steel and mercury in a levitator constructed with off-the-shelf components. The schlieren technique was applied to the TinyLev acoustic levitation system, but it can be applied to visualize the acoustic potential produced by different types of levitation systems.
IEEE PHOTONICS TECHNOLOGY LETTERS, 2018
We present a simple and straightforward method to determine the phase shift between the amplitude... more We present a simple and straightforward method to determine the phase shift between the amplitude modulation (AM) and the frequency modulation (FM) of a laser diode. The approach is based on the measurement of AM and FM signals produced by the dynamical response of a laser diode exposed to weak optical feedback. The AM signal is measured directly on a photodiode detecting the emitted power, and the FM signal is demodulated to intensity modulation through the edge filtering techniques using: 1) a volumetric Bragg grating or 2) a Mach–Zehnder interferometer as filters prior to the signal detection. In this letter, we show experimentally that the phase shift determination unveils the linewidth enhancement factor of semiconductor lasers as predicted by the Lang and Kobayashi theory.
Laser-induced breakdown spectroscopy is presented for trace element detection of liquid samples b... more Laser-induced breakdown spectroscopy is presented for trace element detection of liquid samples by analyzing a single droplet levitated by ultrasonic waves. A single liquid droplet is placed in the node of a standing acoustic wave produced by a uniaxial levitator for further chemical analysis. The acoustic levitator consists of a commercial Langevin-type transducer, attached to a concave mechanical amplifier, and a concave reflector. A micro-syringe was used to manually place individual liquid droplet samples in the acoustic levitation system. For chemical analysis, a laser-induced plasma is produced by focusing a single laser pulse on the levitated water droplet after it partially dries. The performance of the acoustic levitator on micron-sized drop-lets is discussed, and the detection of Ba, Cd, Hg, and Pb at parts per million (milligrams/liter) and sub-parts per million levels is reported. The process, starting from placing the sample in the acoustic levitator and ending on the chemical identification of the traces, takes a few minutes. The approach is particularly interesting in applications demanding limited volumes of liquid samples and relative simple and inexpensive techniques.
Self-mixing interferometry (SMI) represents a robust, self-aligned technique for metrology applic... more Self-mixing interferometry (SMI) represents a robust, self-aligned technique for metrology applications. Recently, it has been shown that the detection of the frequency-modulated (FM) signal enhances the conventional SMI signal based on the amplitude modulation. Here, an all-optical, simple and effective alternative approach to detect the FM self-mixing signal is presented. We demonstrate the enhanced self-mixing approach using a laser diode emitting at 405 nm and a volume Bragg grating (VBG) to map frequency to intensity modulations for further optical detection. Our approach overcomes the spectral range limitation of the edge filtering approach based on molecular absorption filters, since the VBGs can be fabricated at any spectral range.
The use of double-pulse laser-induced breakdown spectroscopy (DP-LIBS) in quantitative analysis g... more The use of double-pulse laser-induced breakdown spectroscopy (DP-LIBS) in quantitative analysis generally depends on standards and calibration curves. To our knowledge, in this Letter, we report the first quantitative analysis based on DP-LIBS at low ablative energies with a self-calibrated method. We compare the effects of plasmas on the calibration-free LIBS technique, generated by DP-LIBS, and the traditional single-pulse (SP) LIBS on a steel sample. Our analyses reveal that when SP-LIBS and DP-LIBS reach comparable emission line intensities, plasma parameters and quantitative analysis are practically the same for both experiments. Additionally, we report the behavior of the emission enhancement of some elements (Fe and Cr) at low ablative pulse energies (0.2–8 mJ) using the orthogonal reheating DP-LIBS configuration.
This article appeared in a journal published by Elsevier. The attached copy is furnished to the a... more This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/copyright Adulterated and fake tequila UV–VIS spectroscopy Based on UV–VIS spectroscopy and chemometric techniques, a screening method is presented with which the studied brands of white and rested tequila can be differentiated among them and on the other hand, adulterate and fake tequilas can be distinguished from the corresponding genuine brands. Eighty bottles of tequila (39 white type and 41 rested type) were studied and purchased at liquor stores; special care was taken to get different batches. Through the use of support vector machine (SVM), principal component analysis (PCA) and linear discriminant analysis (LDA) the studied tequilas were differentiated and classified into 8 sets: 4 sets of white and 4 of rested tequilas; each set corresponded to a specific tequila brand. Seven additional samples with similar labeling than the 80 samples were used to validate the method and it was found that each sample was located within the ellipse of confidence of the corresponding tequila brand. Furthermore, 14 adulterated samples were generated from 2 bottles of tequila, one white and one rested, and they could be distinguishable from the genuine tequila, i.e., they were outside of the corresponding ellipse of confidence. In addition, the screening method here presented was employed to analyze rested tequilas that were purchased on the street market, i.e., fake tequilas, with the same label than 3 of the used brands in this work. These samples were discriminated from the corresponding genuine tequila brand. The results suggested that the reported method could play an important role when a quick, trustworthy and feasible result on site is needed since the test of the spirit takes minutes, affording robustness, reliability and in addition, a skilled worker is not required necessarily to apply the method.
A laser Doppler velocimetry (LDV) sensor using the edge-filter enhanced self-mixing interferometr... more A laser Doppler velocimetry (LDV) sensor using the edge-filter enhanced self-mixing interferometry (ESMI) is presented based on speed measurements of single microparticles. The ESMI detection utilizes an acetylene edge-filter that maps the frequency modulation of a semiconductor laser into an intensity modulation as the laser wavelength is tuned to the steep edge of the absorption profile. In this work, the ESMI signal was analyzed for aerosol particles of different sizes from 1 μm to 10 μm at a distance of 2.5 m. At this operation range, the signal from single particles of all sizes was successfully acquired enabling particle velocity measurements through the Doppler shifted frequency along the beam axis. For the particular case of 10 μm particles, single aerosol particles were still detected at an unprecedented range of 10 m. A theoretical treatment describing the relation between Mie scattering theory and the self-mixing phenomenon on single-particle detection is presented supporting the experimental results. The results show that the edge-filter enhanced self-mixing technique opens new possibilities for self-mixing detection where longer ranges, lower backscattering laser powers and higher velocities are involved. For example, it can be used as a robust and inexpensive anemometer for LDV applications for airflows with low-number density of microparticles.
Self-mixing interferometry (SMI) represents a simple, robust, and self-aligned technique for metr... more Self-mixing interferometry (SMI) represents a simple, robust, and self-aligned technique for metrology applications. Still, its applicability on diffuse targets is limited to distances up to few meters. We present an enhanced approach based on the detection of the frequency-modulated (FM) self-mixing signal. The FM signal detection is achieved using an acetylene edge filter that maps laser frequency variations into intensity variations as the laser wavelength is tuned to the edge of the steep absorption profile. An experimental comparison between the enhanced and the conventional SMI approach is presented. The new approach yields to about two orders of magnitude larger signal-to-noise ratio and extends the applicability of SMI into new fields allowing longer detection ranges and lower backscattering signals.
Airborne acoustic trapping by ultrasonic phased arrays has seen great advances in recent years, a... more Airborne acoustic trapping by ultrasonic phased arrays has seen great advances in recent years, and yet the manipulation of objects with different shapes and sizes or heavy particles remains challenging. Here, we demonstrate that the manipulation capabilities of a standing-wave acoustic levitator can be extended by introducing intracavity high-order transverse (HOT) modes in the azimuthal direction, enabling the simultaneous trapping of several objects within a wide range of shapes and sizes with positional and rotational stability, including objects with sizes larger than one wavelength and weights in the scale of millinewtons. The conditions to generate different HOT modes are theoretically analyzed and experimentally implemented. We numerically calculate the pressure distributions, exhibiting good qualitative agreement with the experimental pressure distributions obtained with schlieren images. In addition, we calculate the acoustic force field for several examples of HOT modes and different particle sizes, which leads to a qualitative understanding of the experimental observations.
Enhanced standing-wave acoustic levitation using high-order transverse modes in phased array ultrasonic cavities, 2024
Airborne acoustic trapping by ultrasonic phased arrays has seen great advances in recent years, a... more Airborne acoustic trapping by ultrasonic phased arrays has seen great advances in recent years, and yet the manipulation of objects with different shapes and sizes or heavy particles remains challenging. Here, we demonstrate that the manipulation capabilities of a standing-wave acoustic levitator can be extended by introducing intracavity high-order transverse (HOT) modes in the azimuthal direction, enabling the simultaneous trapping of several objects within a wide range of shapes and sizes with positional and rotational stability, including objects with sizes larger than one wavelength and weights in the scale of millinewtons. The conditions to generate different HOT modes are theoretically analyzed and experimentally implemented. We numerically calculate the pressure distributions, exhibiting good qualitative agreement with the experimental pressure distributions obtained with schlieren images. In addition, we calculate the acoustic force field for several examples of HOT modes and different particle sizes, which leads to a qualitative understanding of the experimental observations.
Optics letters, Jan 15, 2018
Laser-induced breakdown spectroscopy is presented for trace element detection of liquid samples b... more Laser-induced breakdown spectroscopy is presented for trace element detection of liquid samples by analyzing a single droplet levitated by ultrasonic waves. A single liquid droplet is placed in the node of a standing acoustic wave produced by a uniaxial levitator for further chemical analysis. The acoustic levitator consists of a commercial Langevin-type transducer, attached to a concave mechanical amplifier, and a concave reflector. A micro-syringe was used to manually place individual liquid droplet samples in the acoustic levitation system. For chemical analysis, a laser-induced plasma is produced by focusing a single laser pulse on the levitated water droplet after it partially dries. The performance of the acoustic levitator on micron-sized droplets is discussed, and the detection of Ba, Cd, Hg, and Pb at parts per million (milligrams/liter) and sub-parts per million levels is reported. The process, starting from placing the sample in the acoustic levitator and ending on the ch...
Optics letters, 2017
Self-mixing interferometry (SMI) represents a robust, self-aligned technique for metrology applic... more Self-mixing interferometry (SMI) represents a robust, self-aligned technique for metrology applications. Recently, it has been shown that the detection of the frequency-modulated (FM) signal enhances the conventional SMI signal based on the amplitude modulation. Here, an all-optical, simple and effective alternative approach to detect the FM self-mixing signal is presented. We demonstrate the enhanced self-mixing approach using a laser diode emitting at 405 nm and a volume Bragg grating (VBG) to map frequency to intensity modulations for further optical detection. Our approach overcomes the spectral range limitation of the edge filtering approach based on molecular absorption filters, since the VBGs can be fabricated at any spectral range.
Nova Scientia, 2014
A través de una técnica óptica de espectroscopia basada en la absorción de luz en el rango UV vis... more A través de una técnica óptica de espectroscopia basada en la absorción de luz en el rango UV visible y un análisis estadístico multivariable es posible identificar marcas de tequila para la protección de marca in situ. Se adquirieron 40 muestras de tequilas tipo reposado de 4 marcas registradas en tiendas de licores y en algunos bares en las ciudades de León Gto. y de Zacatecas, Zac. con el propósito de encontrar similitudes y diferencias que permitan una agrupación y una posible predicción de marcas para futuras muestras. Se describe el método para la discriminación de estas bebidas alcohólicas el cual es complementario a los métodos actuales basados en análisis químicos que son mayor coste y complejidad. Los resultados muestran una buena agrupación de las marcas analizadas por lo que una nueva muestra pudiera clasificarse si pertenece o no a alguna de las marcas estudiadas. El análisis de muestras se realiza en tiempos de minutos y pueden realizarse in situ.
Optics express, Jan 18, 2016
A laser Doppler velocimetry (LDV) sensor using the edge-filter enhanced self-mixing interferometr... more A laser Doppler velocimetry (LDV) sensor using the edge-filter enhanced self-mixing interferometry (ESMI) is presented based on speed measurements of single microparticles. The ESMI detection utilizes an acetylene edge-filter that maps the frequency modulation of a semiconductor laser into an intensity modulation as the laser wavelength is tuned to the steep edge of the absorption profile. In this work, the ESMI signal was analyzed for aerosol particles of different sizes from 1 μm to 10 μm at a distance of 2.5 m. At this operation range, the signal from single particles of all sizes was successfully acquired enabling particle velocity measurements through the Doppler shifted frequency along the beam axis. For the particular case of 10 μm particles, single aerosol particles were still detected at an unprecedented range of 10 m. A theoretical treatment describing the relation between Mie scattering theory and the self-mixing phenomenon on single-particle detection is presented suppor...
Optics Letters, 2015
Self-mixing interferometry (SMI) represents a simple, robust, and self-aligned technique for metr... more Self-mixing interferometry (SMI) represents a simple, robust, and self-aligned technique for metrology applications. Still, its applicability on diffuse targets is limited to distances up to few meters. We present an enhanced approach based on the detection of the frequency-modulated (FM) self-mixing signal. The FM signal detection is achieved using an acetylene edge filter that maps laser frequency variations into intensity variations as the laser wavelength is tuned to the edge of the steep absorption profile. An experimental comparison between the enhanced and the conventional SMI approach is presented. The new approach yields to about two orders of magnitude larger signal-to-noise ratio and extends the applicability of SMI into new fields allowing longer detection ranges and lower backscattering signals.
Optics Letters, 2012
The use of double-pulse laser-induced breakdown spectroscopy (DP-LIBS) in quantitative analysis g... more The use of double-pulse laser-induced breakdown spectroscopy (DP-LIBS) in quantitative analysis generally depends on standards and calibration curves. To our knowledge, in this Letter, we report the first quantitative analysis based on DP-LIBS at low ablative energies with a self-calibrated method. We compare the effects of plasmas on the calibration-free LIBS technique, generated by DP-LIBS, and the traditional single-pulse (SP) LIBS on a steel sample. Our analyses reveal that when SP-LIBS and DP-LIBS reach comparable emission line intensities, plasma parameters and quantitative analysis are practically the same for both experiments. Additionally, we report the behavior of the emission enhancement of some elements (Fe and Cr) at low ablative pulse energies (0.2-8 mJ) using the orthogonal reheating DP-LIBS configuration.
Food Research International, 2010
Based on UV-VIS spectroscopy and chemometric techniques, a screening method is presented with whi... more Based on UV-VIS spectroscopy and chemometric techniques, a screening method is presented with which the studied brands of white and rested tequila can be differentiated among them and on the other hand, adulterate and fake tequilas can be distinguished from the corresponding genuine brands. Eighty bottles of tequila (39 white type and 41 rested type) were studied and purchased at liquor stores; special care was taken to get different batches. Through the use of support vector machine (SVM), principal component analysis (PCA) and linear discriminant analysis (LDA) the studied tequilas were differentiated and classified into 8 sets: 4 sets of white and 4 of rested tequilas; each set corresponded to a specific tequila brand. Seven additional samples with similar labeling than the 80 samples were used to validate the method and it was found that each sample was located within the ellipse of confidence of the corresponding tequila brand. Furthermore, 14 adulterated samples were generated from 2 bottles of tequila, one white and one rested, and they could be distinguishable from the genuine tequila, i.e., they were outside of the corresponding ellipse of confidence. In addition, the screening method here presented was employed to analyze rested tequilas that were purchased on the street market, i.e., fake tequilas, with the same label than 3 of the used brands in this work. These samples were discriminated from the corresponding genuine tequila brand. The results suggested that the reported method could play an important role when a quick, trustworthy and feasible result on site is needed since the test of the spirit takes minutes, affording robustness, reliability and in addition, a skilled worker is not required necessarily to apply the method.
IEEE Photonics Technology Letters, 2018
We present a simple and straightforward method to determine the phase shift between the amplitude... more We present a simple and straightforward method to determine the phase shift between the amplitude modulation (AM) and the frequency modulation (FM) of a laser diode. The approach is based on the measurement of AM and FM signals produced by the dynamical response of a laser diode exposed to weak optical feedback. The AM signal is measured directly on a photodiode detecting the emitted power and the FM signal is demodulated to intensity modulation through the edge filtering techniques using (a) a volumetric Bragg grating or (b) a Mach-Zehnder interferometer as filters prior to the signal detection. In this work, we show experimentally that the phase shift determination unveils the linewidth enhancement factor of semiconductor lasers as predicted by the Lang and Kobayashi theory.
Review of Scientific Instruments, 2021
Acoustic levitation uses focused high-intensity airborne ultrasound to hold particles in mid-air.... more Acoustic levitation uses focused high-intensity airborne ultrasound to hold particles in mid-air. It is becoming an important tool for experiments in spectrometry, lab-on-a-droplet, and display technologies. Nowadays, arrays of multiple small transducers can be used to build acoustic levitators; however, their performance depends on the optimal alignment. This work describes a simple method capable of visualizing a 2D projection of the acoustic field in real time using rainbow schlieren deflectometry. Good agreement was found between the images obtained with this technique and simulations of the acoustic pressure. It was also found that the maximum amplitudes of the field were obtained with the levitator aligned so that the power consumption was minimum, showing another simple and affordable way to adjust the levitators. As a result of the alignment optimization, it was possible for the first time to levitate steel and mercury in a levitator constructed with off-the-shelf components. The schlieren technique was applied to the TinyLev acoustic levitation system, but it can be applied to visualize the acoustic potential produced by different types of levitation systems.
IEEE PHOTONICS TECHNOLOGY LETTERS, 2018
We present a simple and straightforward method to determine the phase shift between the amplitude... more We present a simple and straightforward method to determine the phase shift between the amplitude modulation (AM) and the frequency modulation (FM) of a laser diode. The approach is based on the measurement of AM and FM signals produced by the dynamical response of a laser diode exposed to weak optical feedback. The AM signal is measured directly on a photodiode detecting the emitted power, and the FM signal is demodulated to intensity modulation through the edge filtering techniques using: 1) a volumetric Bragg grating or 2) a Mach–Zehnder interferometer as filters prior to the signal detection. In this letter, we show experimentally that the phase shift determination unveils the linewidth enhancement factor of semiconductor lasers as predicted by the Lang and Kobayashi theory.
Laser-induced breakdown spectroscopy is presented for trace element detection of liquid samples b... more Laser-induced breakdown spectroscopy is presented for trace element detection of liquid samples by analyzing a single droplet levitated by ultrasonic waves. A single liquid droplet is placed in the node of a standing acoustic wave produced by a uniaxial levitator for further chemical analysis. The acoustic levitator consists of a commercial Langevin-type transducer, attached to a concave mechanical amplifier, and a concave reflector. A micro-syringe was used to manually place individual liquid droplet samples in the acoustic levitation system. For chemical analysis, a laser-induced plasma is produced by focusing a single laser pulse on the levitated water droplet after it partially dries. The performance of the acoustic levitator on micron-sized drop-lets is discussed, and the detection of Ba, Cd, Hg, and Pb at parts per million (milligrams/liter) and sub-parts per million levels is reported. The process, starting from placing the sample in the acoustic levitator and ending on the chemical identification of the traces, takes a few minutes. The approach is particularly interesting in applications demanding limited volumes of liquid samples and relative simple and inexpensive techniques.
Self-mixing interferometry (SMI) represents a robust, self-aligned technique for metrology applic... more Self-mixing interferometry (SMI) represents a robust, self-aligned technique for metrology applications. Recently, it has been shown that the detection of the frequency-modulated (FM) signal enhances the conventional SMI signal based on the amplitude modulation. Here, an all-optical, simple and effective alternative approach to detect the FM self-mixing signal is presented. We demonstrate the enhanced self-mixing approach using a laser diode emitting at 405 nm and a volume Bragg grating (VBG) to map frequency to intensity modulations for further optical detection. Our approach overcomes the spectral range limitation of the edge filtering approach based on molecular absorption filters, since the VBGs can be fabricated at any spectral range.
The use of double-pulse laser-induced breakdown spectroscopy (DP-LIBS) in quantitative analysis g... more The use of double-pulse laser-induced breakdown spectroscopy (DP-LIBS) in quantitative analysis generally depends on standards and calibration curves. To our knowledge, in this Letter, we report the first quantitative analysis based on DP-LIBS at low ablative energies with a self-calibrated method. We compare the effects of plasmas on the calibration-free LIBS technique, generated by DP-LIBS, and the traditional single-pulse (SP) LIBS on a steel sample. Our analyses reveal that when SP-LIBS and DP-LIBS reach comparable emission line intensities, plasma parameters and quantitative analysis are practically the same for both experiments. Additionally, we report the behavior of the emission enhancement of some elements (Fe and Cr) at low ablative pulse energies (0.2–8 mJ) using the orthogonal reheating DP-LIBS configuration.
This article appeared in a journal published by Elsevier. The attached copy is furnished to the a... more This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/copyright Adulterated and fake tequila UV–VIS spectroscopy Based on UV–VIS spectroscopy and chemometric techniques, a screening method is presented with which the studied brands of white and rested tequila can be differentiated among them and on the other hand, adulterate and fake tequilas can be distinguished from the corresponding genuine brands. Eighty bottles of tequila (39 white type and 41 rested type) were studied and purchased at liquor stores; special care was taken to get different batches. Through the use of support vector machine (SVM), principal component analysis (PCA) and linear discriminant analysis (LDA) the studied tequilas were differentiated and classified into 8 sets: 4 sets of white and 4 of rested tequilas; each set corresponded to a specific tequila brand. Seven additional samples with similar labeling than the 80 samples were used to validate the method and it was found that each sample was located within the ellipse of confidence of the corresponding tequila brand. Furthermore, 14 adulterated samples were generated from 2 bottles of tequila, one white and one rested, and they could be distinguishable from the genuine tequila, i.e., they were outside of the corresponding ellipse of confidence. In addition, the screening method here presented was employed to analyze rested tequilas that were purchased on the street market, i.e., fake tequilas, with the same label than 3 of the used brands in this work. These samples were discriminated from the corresponding genuine tequila brand. The results suggested that the reported method could play an important role when a quick, trustworthy and feasible result on site is needed since the test of the spirit takes minutes, affording robustness, reliability and in addition, a skilled worker is not required necessarily to apply the method.
A laser Doppler velocimetry (LDV) sensor using the edge-filter enhanced self-mixing interferometr... more A laser Doppler velocimetry (LDV) sensor using the edge-filter enhanced self-mixing interferometry (ESMI) is presented based on speed measurements of single microparticles. The ESMI detection utilizes an acetylene edge-filter that maps the frequency modulation of a semiconductor laser into an intensity modulation as the laser wavelength is tuned to the steep edge of the absorption profile. In this work, the ESMI signal was analyzed for aerosol particles of different sizes from 1 μm to 10 μm at a distance of 2.5 m. At this operation range, the signal from single particles of all sizes was successfully acquired enabling particle velocity measurements through the Doppler shifted frequency along the beam axis. For the particular case of 10 μm particles, single aerosol particles were still detected at an unprecedented range of 10 m. A theoretical treatment describing the relation between Mie scattering theory and the self-mixing phenomenon on single-particle detection is presented supporting the experimental results. The results show that the edge-filter enhanced self-mixing technique opens new possibilities for self-mixing detection where longer ranges, lower backscattering laser powers and higher velocities are involved. For example, it can be used as a robust and inexpensive anemometer for LDV applications for airflows with low-number density of microparticles.
Self-mixing interferometry (SMI) represents a simple, robust, and self-aligned technique for metr... more Self-mixing interferometry (SMI) represents a simple, robust, and self-aligned technique for metrology applications. Still, its applicability on diffuse targets is limited to distances up to few meters. We present an enhanced approach based on the detection of the frequency-modulated (FM) self-mixing signal. The FM signal detection is achieved using an acetylene edge filter that maps laser frequency variations into intensity variations as the laser wavelength is tuned to the edge of the steep absorption profile. An experimental comparison between the enhanced and the conventional SMI approach is presented. The new approach yields to about two orders of magnitude larger signal-to-noise ratio and extends the applicability of SMI into new fields allowing longer detection ranges and lower backscattering signals.